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Crystals, Volume 6, Issue 9 (September 2016) – 20 articles

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6557 KiB  
Article
Spacer-Controlled Supramolecular Assemblies of Cu(II) with Bis(2-Hydroxyphenylimine) Ligands. from Monoligand Complexes to Double-Stranded Helicates and Metallomacrocycles
by Norman Kelly, Franziska Taube, Kerstin Gloe, Thomas Doert, Wilhelm Seichter, Axel Heine, Jan J. Weigand and Karsten Gloe
Crystals 2016, 6(9), 120; https://doi.org/10.3390/cryst6090120 - 21 Sep 2016
Cited by 1 | Viewed by 4782
Abstract
Reaction of Cu(NO3)2·3H2O or Cu(CH3COO)2·H2O with the bis(2-hydroxyphenylimine) ligands H2L1-H2L4 gave four Cu(II) complexes of composition [Cu2(L1)(NO3 [...] Read more.
Reaction of Cu(NO3)2·3H2O or Cu(CH3COO)2·H2O with the bis(2-hydroxyphenylimine) ligands H2L1-H2L4 gave four Cu(II) complexes of composition [Cu2(L1)(NO3)2(H2O)]·MeOH, [Cu2(L2)2], [Cu2(L3)2] and [Cu2(L4)2]·2MeOH. Depending on the spacer unit, the structures are characterized by a dinuclear arrangement of Cu(II) within one ligand (H2L1), by a double-stranded [2+2] helical binding mode (H2L2 and H2L3) and a [2 + 2] metallomacrocycle formation (H2L4). In these complexes, the Cu(II) coordination geometries are quite different, varying between common square planar or square pyramidal arrangements, and rather rare pentagonal bipyramidal and tetrahedral geometries. In addition, solution studies of the complex formation using UV/Vis and ESI-MS as well as solvent extraction are reported. Full article
(This article belongs to the Special Issue Crystal Structure of Complex Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>ORTEP drawing (50% probability level) of the molecular structure of: [Cu<sub>2</sub>(<b>L<sup>1</sup></b>)(NO<sub>3</sub>)<sub>2</sub>(H<sub>2</sub>O)]·MeOH (<b>a</b>); and simplified stick representation (<b>b</b>).</p>
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<p>Formation of complex dimers and polymeric strands by [Cu<sub>2</sub>(<b>L<sup>1</sup></b>)(NO<sub>3</sub>)<sub>2</sub>(H<sub>2</sub>O)]·MeOH via hydrogen bonding and π···π interactions.</p>
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<p>Packing of [Cu<sub>2</sub>(<b>L<sup>1</sup></b>)(NO<sub>3</sub>)<sub>2</sub>(H<sub>2</sub>O)]·MeOH showing the disordered methanol molecules in the void space.</p>
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<p>ORTEP drawing (50% probability level) of the molecular structure of: [Cu<sub>2</sub>(<b>L<sup>2</sup></b>)<sub>2</sub>] (<b>a</b>); and a simplified stick representation of the helicate (<b>b</b>).</p>
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<p>Intermolecular CH···π and π···π interactions in [Cu<sub>2</sub>(<b>L<sup>2</sup></b>)<sub>2</sub>] resulting in the formation of 2D layers (<b>a</b>); and the resulting packing motif with complex molecules of consistent handedness in the same color (<b>b</b>).</p>
Full article ">Figure 6
<p>ORTEP drawing (50% probability level) of the molecular structure of: [Cu<sub>2</sub>(<b>L<sup>3</sup></b>)<sub>2</sub>] (<b>a</b>); and stick representation of the helicate (<b>b</b>).</p>
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<p>Illustration of the formation of polymeric strands by [Cu<sub>2</sub>(<b>L<sup>3</sup></b>)<sub>2</sub>] involving Cu(II)···π interactions.</p>
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<p>2D layers within the <span class="html-italic">bc</span>-plane in [Cu<sub>2</sub>(<b>L<sup>3</sup></b>)<sub>2</sub>].</p>
Full article ">Figure 9
<p>ORTEP drawing of the molecular structure of [Cu<sub>2</sub>(<b>L<sup>4</sup></b>)<sub>2</sub>]·2MeOH (Ellipsoids are given at the 50% probability level; disordered CH<sub>3</sub>OH is not shown) and the corresponding space fill and capped stick representations.</p>
Full article ">Figure 10
<p>Hydrogen bonds, CH···π and π···π interactions between adjacent metallomacrocycles in [Cu<sub>2</sub>(<b>L<sup>4</sup></b>)<sub>2</sub>]·2MeOH.</p>
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<p>Different orientations of the metallomacrocycles in the <span class="html-italic">bc</span>-plane in [Cu<sub>2</sub>(<b>L<sup>4</sup></b>)<sub>2</sub>]·2MeOH.</p>
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<p>UV/Vis spectra (<b>a</b>) and <span class="html-italic">Job</span> plot (560 nm) (<b>b</b>) for the complexation of Cu(II) with <b>H<sub>2</sub>L<sup>1</sup></b> in dichloromethane/methanol (v/v = 1:1); [<b>H<sub>2</sub>L<sup>1</sup></b>] + [Cu(II)] = 3 × 10<sup>−3</sup> M (<span class="html-italic">x</span><sub>Cu(II)</sub> = 0–1), <span class="html-italic">t</span> = 30 min. (copper(II) acetate spectrum in blue, ligand spectrum in orange).</p>
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<p>Liquid-liquid extraction of Cu(II) by <b>H<sub>2</sub>L<sup>1</sup></b>, <b>H<sub>2</sub>L<sup>2</sup></b>, <b>H<sub>2</sub>L<sup>3</sup></b> and <b>H<sub>2</sub>L<sup>4</sup></b> at pH = 7.7 (HEPES/NaOH buffer); [Cu(II)] = 1 × 10<sup>−</sup><sup>4</sup> M, [NaNO<sub>3</sub>] = 5 × 10<sup>−</sup><sup>3</sup> M; [L] = 1 × 10<sup>−</sup><sup>3</sup> M in CHCl<sub>3</sub>; t = 30 min, T = 22 ± 1 °C.</p>
Full article ">Scheme 1
<p>Structural formulas of <b>H<sub>2</sub>L<sup>1</sup></b>-<b>H<sub>2</sub>L<sup>4</sup></b>.</p>
Full article ">
1993 KiB  
Concept Paper
Two-Level Electron Excitations and Distinctive Physical Properties of Al-Cu-Fe Quasicrystals
by Alexandre Prekul and Natalya Shchegolikhina
Crystals 2016, 6(9), 119; https://doi.org/10.3390/cryst6090119 - 19 Sep 2016
Cited by 7 | Viewed by 4609
Abstract
This article is not a review in the conventional sense. Rather, it is a monographic study of the implications of detection in Al-Cu-Fe quasicrystals of the electronic heat capacity contributions associated with the two-level electron excitations. Our aim was to reveal correlations between [...] Read more.
This article is not a review in the conventional sense. Rather, it is a monographic study of the implications of detection in Al-Cu-Fe quasicrystals of the electronic heat capacity contributions associated with the two-level electron excitations. Our aim was to reveal correlations between these contributions, on the one hand, and specific features of electron transport, magnetic susceptibility, Hall-effect, tunnelling and optical spectra, on the other hand. It is shown that the full range of these features can be understood in the framework of the unified conceptual scheme based on two-level electron excitations. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Figure 1

Figure 1
<p>Temperature dependence of the excess electronic heat capacity of the Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub> quasicrystalline alloy with respect to the Sommerfeld metallic contribution. Solid lines show the approximation of the curve by two Schottky contributions with excitation energies of 0.02 and 0.25 eV.</p>
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<p>Curves of temperature-induced increments in theelectrical conductivity Δσ (open circles), paramagneticsusceptibility Δχ (closed circles), and internal energy ΔU(solid line) of the Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub> icosahedral phase in thetemperature range from 1.8 to 1000 K.</p>
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<p>Change of regimes of thermal activation is a character feature of: two-level excitation density (<b>a</b>); conductivity (<b>b</b>); magnetic susceptibility (<b>c</b>); and inverse Hall effect (<b>d</b>) in the Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub> phase.</p>
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<p>Visual comparison of the local and averaged tunnel spectra obtained in [<a href="#B32-crystals-06-00119" class="html-bibr">32</a>] and the excess electronic specific heat obtained in [<a href="#B25-crystals-06-00119" class="html-bibr">25</a>]. Arrows indicate features similar in shape and energy.</p>
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<p>Deconvolution of the local G(V) curve into elementary terms with the characteristic splitting energies of the levels δE<sub>i</sub> = 5, 16, 80, and 260 meV. The thin solid line is the experimental curve [<a href="#B32-crystals-06-00119" class="html-bibr">32</a>]. The dash-dotted lines are the elementary terms. The thick solid line is the sum of the terms. The dotted lines are residuals after subtraction of the terms.</p>
Full article ">Figure 6
<p>The averaged experimental G(V) curve (thin solid line [<a href="#B32-crystals-06-00119" class="html-bibr">32</a>]) and its description (thick solid line) by the sum of the elementary terms with δE<sub>i</sub> = 5, 16, 80, 260, 400, 1400, and 5300 meV. The dash-dotted lines are the low-energy (LE) part of the spectrum and additional terms. The dotted lines are residuals after subtraction of the calculated curves.</p>
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<p>(<b>a</b>) Experimental optical conductivity of icosahedral Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub> (thin solid line [<a href="#B39-crystals-06-00119" class="html-bibr">39</a>]). The dash-dotted line (1400) is a fit with the Lorentzian peak according to Equation (8). The dotted line is a residue after subtraction of the peak. Dash-dotted line (5300) is a fit with the Lorentzian peak according to Equation (8). Thick solid line is a fit with a sum of this Lorentzian peak and peaks in (<b>b</b>). (<b>b</b>) The residue shown in (<b>a</b>) but on an enlarged scale (solid line). Dash-dotted lines (20, 90, 250, and 420) are the fit with the Lorentzian peaks according to Equation (8).</p>
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<p>Temperature-dependent part of the magnetic susceptibility of the ordered Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub>phase: (o), experimental results [<a href="#B2-crystals-06-00119" class="html-bibr">2</a>]; and solid line, description of the results by a sum of the magnetic elementary terms (dash-dotted lines) with δE = 5, 16, 80, 260, 400, and 1500 meV, respectively.</p>
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<p>Temperature-dependent part of the dc conductivity of the ordered Al<sub>63</sub>Cu<sub>25</sub>Fe<sub>12</sub> phase: (o), experimental results [<a href="#B2-crystals-06-00119" class="html-bibr">2</a>]; and solid line, description of the results by a sum of the conduction elementary terms (dash-dotted lines) with δE = 5, 16, 80, 260, 400, and 1500 meV, respectively.</p>
Full article ">Figure 10
<p>An updated version of the electronic structure model. Shown schematically is the superposition of two types of spectra: the continuum spectrum with a pseudogap and the discrete spectrum with seven types of two-level states. The Fermi level is fixed at the centre of the smallest gap separating the symmetric and antisymmetric states. For the sake of representativity, a nonlinear scale E<sup>1/2</sup> is used. To simplify, only the smallest (δE<sub>1</sub>) and the largest (δE<sub>7</sub>) gaps are indicated by arrows.</p>
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1396 KiB  
Editorial
Boron-Based (Nano-)Materials: Fundamentals and Applications
by Umit B. Demirci, Philippe Miele and Pascal G. Yot
Crystals 2016, 6(9), 118; https://doi.org/10.3390/cryst6090118 - 19 Sep 2016
Cited by 6 | Viewed by 6100
Abstract
The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes [...] Read more.
The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes and carboranes, boronate anions/ligands, boron nitride (hexagonal structure), and elemental boron are considered. Importantly, large sections are dedicated to fundamentals, with a special focus on crystal structures. The application potentials are widely discussed on the basis of the materials’ physical and chemical properties. It stands out that crystalline boron-based (nano-)materials have many technological opportunities in fields such as energy storage, gas sorption (depollution), medicine, and optical and electronic devices. The present special issue is further evidence of the wealth of boron science, especially in terms of crystalline (nano-)materials. Full article
(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)
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Figure 1

Figure 1
<p>Molecular structure of substituted spirobiphenalenyl boron radicals. Adapted from reference [<a href="#B4-crystals-06-00118" class="html-bibr">4</a>]. Reproduced with permission from reference [<a href="#B4-crystals-06-00118" class="html-bibr">4</a>], published by MDPI, 2016.</p>
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<p>View of the packing of molecules in crystals of the phosphane borane adduct (denoted <b>4</b>) along the crystallographic <span class="html-italic">b</span> axis, and view of its molecular structure. Adapted from reference [<a href="#B10-crystals-06-00118" class="html-bibr">10</a>]. Reproduced with permission from reference [<a href="#B10-crystals-06-00118" class="html-bibr">10</a>], published by MDPI, 2016.</p>
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<p>Anionic polyhedral boron hydrides discussed by Avdeeva et al. in reference [<a href="#B16-crystals-06-00118" class="html-bibr">16</a>]. Reproduced with permission from reference [<a href="#B16-crystals-06-00118" class="html-bibr">16</a>], published by MDPI, 2016.</p>
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<p>Representation of the structures of boronic acid/boronate (left); and benzoxaborole/benzoxaborolate (right). Only the tetrahedral-boron forms of boronate/benzoxaborolate anions are shown here. Adapted from reference [<a href="#B17-crystals-06-00118" class="html-bibr">17</a>]. Reproduced with permission from reference [<a href="#B17-crystals-06-00118" class="html-bibr">17</a>], published by MDPI, 2016.</p>
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<p>Representation of the structure of hexagonal boron nitride, the nitrogen atoms are represented in blue, and the boron atoms in pink.</p>
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3226 KiB  
Article
Self-Assembly of Gold Nanocrystals into Discrete Coupled Plasmonic Structures
by Carola Schopf, Ethel Noonan, Aidan J. Quinn and Daniela Iacopino
Crystals 2016, 6(9), 117; https://doi.org/10.3390/cryst6090117 - 14 Sep 2016
Cited by 6 | Viewed by 6289
Abstract
Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for [...] Read more.
Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for fabrication of gold plasmonic structures of controlled stoichiometry obtained by the use of a di-rhenium thio-isocyanide complex as linker molecule for gold nanocrystals. Correlated scanning electron microscopy (SEM)—dark-field spectroscopy was used to characterize obtained discrete monomer, dimer and trimer plasmonic molecules. Polarization-dependent scattering spectra of dimer structures showed highly polarized scattering response, due to their highly asymmetric D∞h geometry. In contrast, some trimer structures displayed symmetric geometry (D3h), which showed small polarization dependent response. Theoretical calculations were used to further understand and attribute the origin of plasmonic bands arising during linker-induced formation of plasmonic molecules. Theoretical data matched well with experimentally calculated data. These results confirm that obtained gold superstructures possess properties which are a combination of the properties arising from single components and can, therefore, be classified as plasmonic molecules. Full article
(This article belongs to the Special Issue Colloidal Nanocrystals: Synthesis, Characterization and Application)
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Figure 1

Figure 1
<p>(<b>a</b>) UV-vis spectra of gold nanoparticles with increasing amount of added Rhenium ligand showing progressive formation of n-mers. Inset: Representative SEM images of formed n-mers (scale bar: 100 nm); (<b>b</b>) SEM image of formed n-mers deposited on SiO<sub>2</sub> substrate; (<b>c</b>) statistical analysis of formed gold nanocrystal structures.</p>
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<p>Scattering spectra of (<b>a</b>) a monomer; (<b>b</b>) a dimer; (<b>c</b>) a trimer gold nanocrystal structures. Experimental data (black) and calculated (red) spectra. Top row: Correlated SEM images of the corresponding structures.</p>
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<p>(<b>a</b>) and (<b>b</b>) polarization resolved scattering spectra of a 60nm gold nanoparticle dimer and trimer. (<b>c</b>) and (<b>d</b>) SEM images of the analyzed nanoparticle dimer and trimer overlaid with the transversal and longitudinal peak plasmon intensity in dependence of the polarizer angle.</p>
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<p>Schematic of a discretised 60 nm gold nanoparticle monomer (<b>a</b>), dimer (<b>b</b>) and trimer (<b>c</b>) with the considered incident light propagation directions (rainbow coloured arrow) and polarisation directions (blue and red double arrows) dependent on the nanostructure symmetry. Calculated scattering spectra for 60 nm gold nanoparticle monomers (<b>d</b>), dimers (<b>e</b>) and trimers (<b>f</b>) for the in panel (a–c) indicated incident light conditions (notation: pol/dir).</p>
Full article ">Scheme 1
<p>Molecular structure of Re<sub>2</sub>(DMAA)<sub>4</sub>(NCS)<sub>2</sub> and schematic of n-mers formation.</p>
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4597 KiB  
Article
The Effect of Twin Grain Boundary Tuned by Temperature on the Electrical Transport Properties of Monolayer MoS2
by Luojun Du, Hua Yu, Li Xie, Shuang Wu, Shuopei Wang, Xiaobo Lu, Mengzhou Liao, Jianling Meng, Jing Zhao, Jing Zhang, Jianqi Zhu, Peng Chen, Guole Wang, Rong Yang, Dongxia Shi and Guangyu Zhang
Crystals 2016, 6(9), 115; https://doi.org/10.3390/cryst6090115 - 14 Sep 2016
Cited by 20 | Viewed by 8458
Abstract
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum [...] Read more.
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum disulphide with a twin grain boundary was grown in our developed low-pressure chemical vapor deposition (CVD) system, and we investigated how the twin GB affects the electrical transport properties of MoS2 by temperature-dependent transport studies. At low temperature, the twin GB can increase the in-plane electrical conductivity of MoS2 and the transport exhibits variable-range hopping (VRH), while at high temperature, the twin GB impedes the electrical transport of MoS2 and the transport exhibits nearest-neighbor hopping (NNH). Our results elucidate carrier transport mechanism of twin GB and give an important indication of twin GB in tailoring the electronic properties of MoS2 for its applications in next-generation electronics and optoelectronic devices. Full article
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Figure 1

Figure 1
<p>(<b>a</b>) Optical reflection image of MoS<sub>2</sub> on a SiO<sub>2</sub> (300 nm)/Si substrate. The image contrast has been increased for visibility; violet is the bare substrate, and blue represents monolayer MoS<sub>2</sub>. (<b>b</b>) An atomistic model of the MoS<sub>2</sub> with twin GB. The black spots are Mo atoms; the yellow spots are two stacked S atoms. The region marked with blue frame line in (<b>a</b>) and (<b>b</b>) is the twin GB.</p>
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<p>(<b>a</b>) SEM image of a device with four electrodes contacting two coalesced MoS<sub>2</sub> grains, G<sub>L</sub>, GB, and G<sub>R</sub> represent the left grain, grain boundary, and right grain; (<b>b</b>) AFM image of region shown in (<b>a</b>); (<b>c</b>) Raman spectra and atomic displacements of the typical Raman-active modes; and (<b>d</b>) PL spectra and the band structure shows the valence band splitting at the K point of the Brillouin zone; the dashed line is the Lorentz fitting.</p>
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<p>(<b>a</b>,<b>b</b>) Output characteristics at 80 K and 430 K, respectively; (<b>c</b>) temperature dependence of electrical conductivity σ; and (<b>d</b>) relative conductivity R<sub>σ</sub> at different temperatures.</p>
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<p>(<b>a</b>,<b>b</b>) Transfer characteristics at 80 K and 430 K, respectively; (<b>c</b>) temperature dependence of mobility μ; and (<b>d</b>) the relation between mobility μ and conductivity σ.</p>
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<p>(<b>a</b>) Temperature dependence of conductivity and variable range hopping. The solid lines are the linear fit to the data that indicate VRH behavior at low temperature; and (<b>b</b>) temperature dependence of conductivity and nearest-neighbor hopping. The solid lines are the linear fit to the data and indicate NNH behavior at high temperature.</p>
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2508 KiB  
Communication
Numerical Analysis of the Combined Influence of Accelerated Crucible Rotation and Dynamic Crucible Translation on Liquid Phase Diffusion Growth of SiGe
by Mandeep Sekhon, Brian Lent and Yanbao Ma
Crystals 2016, 6(9), 116; https://doi.org/10.3390/cryst6090116 - 13 Sep 2016
Cited by 1 | Viewed by 4437
Abstract
The effects of accelerated crucible rotation technique (ACRT) and dynamic translation on liquid phase diffusion (LPD) growth of SixGe1−x single crystals have been separately investigated numerically in earlier works and were found to have a very positive impact on the [...] Read more.
The effects of accelerated crucible rotation technique (ACRT) and dynamic translation on liquid phase diffusion (LPD) growth of SixGe1−x single crystals have been separately investigated numerically in earlier works and were found to have a very positive impact on the LPD growth process. Building upon these findings, in this paper, we study the consequences of imposing both ACRT and dynamic translation on this growth technique. Time-dependent, axisymmetric numerical simulations using moving grid approach have been carried out using finite volume code Ansys Fluent. Crucible translation effect is simulated using dynamic thermal boundary condition. Results are compared to the case in which this growth system is subjected to ACRT only. It is predicted that by combining ACRT with dynamic pulling, excellent axial compositional uniformity can be achieved and growth rate can be improved substantially without significantly compromising on the benefits of employing ACRT. The results show that it is advantageous to utilize the combination of ACRT and dynamic translation during LPD growth rather than using them independently for producing relatively uniform composition SixGe1−x single crystals in a shorter span of time. Full article
(This article belongs to the Special Issue Global Modeling in Crystal Growth)
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Figure 1
<p>Initial computational mesh used for numerical simulation in the (<b>a</b>) Liquid subdomain (<b>b</b>) Solid subdomains.</p>
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<p>Maximum outward and inward radial velocities in the vicinity of the growth interface after 6 h of growth time.</p>
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<p>Difference between crystal composition at the wall and at the centerline along the growth interface.</p>
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<p>Difference between temperature at the wall and at the centerline along the growth interface.</p>
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<p>Variation of the interface temperature at the centerline with growth time after the initiation of dynamic translation (t = 5 h).</p>
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<p>Variation of the axial crystal composition at the centerline after the initiation of dynamic translation (t = 5 h).</p>
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<p>Growth velocity variation at the centerline during a single ACRT cycle at t = 7 h.</p>
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<p>Interface displacement in 7 h of growth time (<b>a</b>) ACRT, (<b>b</b>) ACRT with dynamic translation.</p>
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<p>Dynamic pull profile between t = 5 h and t = 7 h.</p>
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2775 KiB  
Article
Synthesis of Novel p-tert-Butylcalix[4]arene Derivative: Structural Characterization of a Methanol Inclusion Compound
by Silvana Moris, Antonio Galdámez, Paul Jara and Claudio Saitz-Barria
Crystals 2016, 6(9), 114; https://doi.org/10.3390/cryst6090114 - 9 Sep 2016
Cited by 6 | Viewed by 5977
Abstract
A p-tertbutylcalix[4]arene derivative was synthesized from a reaction of the diisothiocyanate p-tertbutylcalix[4]arene, obtaining crystals that were then characterized by mass spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. The molecule presents two acid carbamothioic-n-ethoxy-methyl-ester substituent groups. Through crystallization of this compound, it [...] Read more.
A p-tertbutylcalix[4]arene derivative was synthesized from a reaction of the diisothiocyanate p-tertbutylcalix[4]arene, obtaining crystals that were then characterized by mass spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. The molecule presents two acid carbamothioic-n-ethoxy-methyl-ester substituent groups. Through crystallization of this compound, it was also found that it includes a methanol molecule within the aromatic cavity. The inclusion of the methanol molecule is due to favorable CH∙∙∙π interactions. Full article
(This article belongs to the Section Biomolecular Crystals)
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Graphical abstract

Graphical abstract
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<p>(<b>top</b>) Positive ion ESI-MS of compound (<b>3</b>); 819.4217 (M + H<sup>+</sup>) (<b>a</b>) (MW819), (<b>b</b>) (MW836) X + NH<sub>4</sub><sup>+</sup> and (<b>c</b>) (MW 841) X + Na<sup>+</sup> (<b>bottom</b>) Positive ion ESI-MS of compound (<b>4</b>); 883.4757 (<b>a</b>) (MW883) M + H<sup>+</sup>, (<b>b</b>) (MW900) M + NH<sub>4</sub><sup>+</sup> and (<b>c</b>) M + Na<sup>+</sup>.</p>
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<p>Raman spectra of compounds (<b>1</b>), (<b>3</b>), and (<b>4</b>) in solid state. The insert shows the C=N stretching band.</p>
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<p>Crystal structure of compound (<b>4</b>). Some H-atoms has been omitted by clarity.</p>
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<p>Dimers of compound (<b>4</b>). The methanol solvent molecule and H atoms not involved in the intermolecular interactions have been omitted for clarity.</p>
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<p>View of intramolecular interactions in compound (<b>4</b>). The H atoms not involved in the intermolecular interactions and the solvent methanol molecule have been omitted for clarity.</p>
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<p>View of intermolecular interactions in compound (<b>4</b>): (<b>top</b>) Cavity and a methanol molecule through interaction of C-H···π. (<b>bottom</b>) N-H···π interactions. The H-atoms not involved in the intermolecular interactions have been omitted for clarity.</p>
Full article ">Scheme 1
<p>Representative diagram of the synthesis of compound (<b>4</b>): (<b>a</b>) K<sub>2</sub>CO<sub>3</sub>, BrCH<sub>2</sub>CN, CH<sub>3</sub>CN, reflux, 8 h; (<b>b</b>) LiAlH<sub>4</sub>, THF, N<sub>2,</sub> 4 h; (<b>c</b>) BaCO<sub>3</sub> CH<sub>2</sub>Cl<sub>2</sub> and thiophosgene, 24 h at RT; (<b>d</b>) hot CHCl<sub>3</sub>/CH<sub>3</sub>OH at R.T.</p>
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5821 KiB  
Review
Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates
by Han Huang, Yingbao Huang, Shitan Wang, Menglong Zhu, Haipeng Xie, Lei Zhang, Xiaoming Zheng, Qiliang Xie, Dongmei Niu and Yongli Gao
Crystals 2016, 6(9), 113; https://doi.org/10.3390/cryst6090113 - 9 Sep 2016
Cited by 25 | Viewed by 11160
Abstract
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress [...] Read more.
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW) heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc), perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and dioctylbenzothienobenzothiophene (C8-BTBT)) and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN)). The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed. Full article
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<p>Molecular structures of pentacene (<b>a</b>), CuPc (<b>b</b>), PTCDA (<b>c</b>), C<sub>8</sub>-BTBT (<b>d</b>), respectively. (<b>e</b>) The a-b and b-c planes of a pentacene single crystal, showing the anisotropy of small organic molecules. (<b>f</b>) Schematics of three layered substrates, G, MoS<sub>2</sub> and <span class="html-italic">h</span>-BN.</p>
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<p>Morphologies of pentacene thin films on different substrates. (<b>a</b>) AFM topography image of fractal islands of pentacene on SiO<sub>2</sub> at a coverage of ~3 ML. Inset: nucleation at submonolayer coverage. (<b>b</b>) STM image of pentacene on Bi(001) at a coverage of slightly over 1 ML. Inset: high-resolution STM image showing pentacene molecules in the first layer in a standing-up configuration. (<b>c</b>) Twelve nanometer thick pentacene film on Highly Oriented Pyrolytic Graphite (HOPG). (<b>d</b>–<b>f</b>) Schematic representations of the proposed molecular packing corresponding to image in panel (<b>a</b>–<b>c</b>). Panel a reprinted with permission from [<a href="#B12-crystals-06-00113" class="html-bibr">12</a>]. Copyright 2004 American Chemical Society. Panel b reprinted from [<a href="#B8-crystals-06-00113" class="html-bibr">8</a>] with the permission of AIP Publishing. Panels c, f reprinted with permission from [<a href="#B6-crystals-06-00113" class="html-bibr">6</a>] as follows: Koch, N. Physical review letters, 96 (15), 156803, 2006. Copyright 2006, American Physical Society.</p>
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<p>Epitaxial growth of pentacene molecular crystals on layered substrates. (<b>a</b>) AFM image of ~50 nm thick pentacene films over the sharp linear boundary between G-covered and bare SiO<sub>2</sub>. (<b>b</b>) Forty nanometer pentacene films over the boundary between MoS<sub>2</sub>-covered and bare SiO<sub>2</sub>. (<b>c</b>) Approximately two ML pentacene crystals with a flat-lying wetting layer on mechanically exfoliated <span class="html-italic">h</span>-BN. (<b>d</b>–<b>f</b>) Schematic illustrations of the molecular packing of (<b>a</b>–<b>c</b>), respectively. (<b>g</b>–<b>i</b>) The transfer characteristics of FETs based on the films in (<b>a</b>–<b>c</b>), respectively. Panel a,d,g reprinted with permission from [<a href="#B15-crystals-06-00113" class="html-bibr">15</a>]. Copyright 2011 American Chemical Society. Panel b, h reprinted with permission from [<a href="#B40-crystals-06-00113" class="html-bibr">40</a>]. Copyright 2015 American Chemical Society. Panel c, f, i reprinted with permission from [<a href="#B7-crystals-06-00113" class="html-bibr">7</a>] as follows: Zhang, Y. Physical review letters, 116 (1), 016602, 2016. Copyright 2016 American Physical Society.</p>
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<p>The AFM morphologic images and 2D-GIXRD images of CuPc on glass (<b>a,d</b>), G-covered glass (<b>b,e</b>), and bulk MoS<sub>2</sub> (<b>c,f</b>), respectively. The insets show the corresponding CuPc packing. Panel a, b, d, e is reproduced from [<a href="#B45-crystals-06-00113" class="html-bibr">45</a>] with permission from The Royal Society of Chemistry. Panel c, f is reprinted with permission from [<a href="#B50-crystals-06-00113" class="html-bibr">50</a>], copyright 2015 American Chemical Society.</p>
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<p>(<b>a</b>) Raman spectra from pentacene on glass without/with monolayer G, and from G on glass. (λ = 532 nm; 3.0 mW). (<b>b</b>) Raman spectra from 2 Å thick CuPc on G (blue line), on <span class="html-italic">h</span>-BN (red line), on MoS<sub>2</sub> (green line), and on the blank SiO<sub>2</sub>/Si substrate (black line). Panel a reprinted with permission from [<a href="#B36-crystals-06-00113" class="html-bibr">36</a>], copyright 2015 American Chemical Society. Panel b reprinted with permission from [<a href="#B55-crystals-06-00113" class="html-bibr">55</a>], copyright 2015 American Chemical Society.</p>
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<p>C<sub>8</sub>-BTBT on layered substrates. AFM image of C<sub>8</sub>-BTBT on G (<b>a</b>) and MoS<sub>2</sub> (<b>b</b>). (<b>c</b>) Transfer characteristic of 1L C<sub>8</sub>-BTBT/<span class="html-italic">h</span>-BN based planar OFET at room temperature. Black and blue lines are drawn in linear and log scales, respectively. Inset shows the optical microscopy image of the device. (<b>d</b>) Blue dots: calculated binding energies of a single C<sub>8</sub>-BTBT molecule on G, IL/G, 1L/IL/G, and 2L/1L/IL/G. Red dash line: C<sub>8</sub>-BTBT−C<sub>8</sub>-BTBT interaction. Inset shows the molecular structure of C<sub>8</sub>-BTBT and molecular packing of different C<sub>8</sub>-BTBT layers on G. (<b>e</b>) AFM images of SLOMBE of bilayer C<sub>8</sub>-BTBT on PTCDA. (<b>f</b>) Output characteristics of the p-n junction (&gt;15 nm) under the dark conditions (black) and under the 0.67 μW laser illumination. Inset shows schematic layout of the device. Panel a, c reprinted with permission from [<a href="#B56-crystals-06-00113" class="html-bibr">56</a>], copyright 2014, Nature Publishing Group. Panel b reprinted from [<a href="#B57-crystals-06-00113" class="html-bibr">57</a>], with the permission of AIP Publishing. Panel d, e, f adapted with permission from [<a href="#B67-crystals-06-00113" class="html-bibr">67</a>], copyright 2016 American Chemical Society.</p>
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<p>PTCDA on layered substrates. (<b>a</b>) Molecularly-resolved STM image of one monolayer PTCDA covered epitaxial G on SiC(0001). (<b>b</b>) STM image of ~0.01 ML Fe (protrusions) on one monolayer PTCDA covered Bi2Se3 (<b>left</b>) and STS curves at positions with/without Fe (purple/black, <b>right</b>). (<b>c</b>) STS curves at positions of PTCDA on Au(111), graphite, and WSe2/graphite. Panel a printed with permission from [<a href="#B68-crystals-06-00113" class="html-bibr">68</a>], copyright 2009 American Chemical Society. Panel b printed with permission from [<a href="#B69-crystals-06-00113" class="html-bibr">69</a>], copyright 2015 American Chemical Society. Panel c printed with permission from [<a href="#B70-crystals-06-00113" class="html-bibr">70</a>], copyright 2016 American Chemical Society.</p>
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2351 KiB  
Article
Coupled Acoustic-Mechanical Bandgaps
by Jakob S. Jensen and Junghwan Kook
Crystals 2016, 6(9), 112; https://doi.org/10.3390/cryst6090112 - 8 Sep 2016
Cited by 3 | Viewed by 4395
Abstract
In this work, we study the existence of coupled bandgaps for corrugated plate structures and acoustic channels. The study is motivated by the observation that the performance of traditional bandgap structures, such as periodic plates, may be compromised due to the coupling to [...] Read more.
In this work, we study the existence of coupled bandgaps for corrugated plate structures and acoustic channels. The study is motivated by the observation that the performance of traditional bandgap structures, such as periodic plates, may be compromised due to the coupling to a surrounding acoustic medium and the presence of acoustic resonances. It is demonstrated that corrugation of the plate structure can introduce bending wave bandgaps and bandgaps in the acoustic domain in overlapping and audible frequency ranges. This effect is preserved also when taking the physical coupling between the two domains into account. Additionally, the coupling is shown to introduce extra gaps in the band structure due to modal interaction and the appearance of a cut-on frequency for the fundamental acoustic mode. Full article
(This article belongs to the Special Issue Phononic Crystals)
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Figure 1
<p>A planar bi-material unit cell consisting of a soft and flexible matrix material (grey) and a heavy stiff inclusion.</p>
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<p>Band diagram for the pure plate structure (solid lines with stars) and for the coupled plate-acoustic model: ASI (discrete circles).</p>
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<p>A finite plate structure with <math display="inline"> <semantics> <mrow> <mn>10</mn> <mo>×</mo> <mn>10</mn> </mrow> </semantics> </math> unit cells and a top acoustic layer of <math display="inline"> <semantics> <mrow> <mi>h</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>005</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>m.</p>
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<p>(<b>a</b>) Vertical vibration amplitude near the corner point opposite the corner of excitation, with and without acoustic coupling (ASI); (<b>b</b>) pressure amplitude at the opposite corner in the case of acoustic coupling.</p>
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<p>Layout and definition of geometrical parameters for the combined corrugated plate/acoustic channel.</p>
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<p>(<b>a</b>) Band structure for a homogenous channel; (<b>b</b>) band structure for an inhomogeneous channel with discrete markers representing results for the first band obtained using Comsol. Unit cell length: <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>=</mo> <mn>1</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>cm.</p>
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<p>(<b>a</b>) Band structure for a homogenous plate; (<b>b</b>) band structure for an inhomogeneous plate with markers representing results for the first band obtained using Comsol (2D solid model). Unit cell length: <math display="inline"> <semantics> <mrow> <mi>L</mi> <mo>=</mo> <mn>1</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>cm.</p>
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<p>(<b>a</b>) Band diagrams based on an uncoupled analysis of acoustic and structural wave propagation; (<b>b</b>) band diagrams based on fully-coupled analysis.</p>
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<p>Frequency (velocity) response for finite structures with 10 unit cells: (<b>a</b>) for a structure corresponding to <a href="#crystals-06-00112-f010" class="html-fig">Figure 10</a>b; (<b>b</b>) for a structure with an increased air gap and a smaller overlapping bandgap.</p>
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<p>Results for a thin (<math display="inline"> <semantics> <mrow> <msub> <mi>t</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>50</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>mm and <math display="inline"> <semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>2</mn> <mo>.</mo> <mn>50</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>mm) and light plate (<math display="inline"> <semantics> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>1000</mn> <mspace width="0.166667em"/> </mrow> </semantics> </math>kg/m<math display="inline"> <semantics> <msup> <mrow/> <mn>3</mn> </msup> </semantics> </math>). (<b>a</b>) Band diagrams based on fully-coupled analysis; (<b>b</b>) fully-coupled analysis based on a Comsol model with a 2D solid model.</p>
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5742 KiB  
Article
Symmetry-Induced Light Confinement in a Photonic Quasicrystal-Based Mirrorless Cavity
by Gianluigi Zito, Giulia Rusciano, Antonio Sasso and Sergio De Nicola
Crystals 2016, 6(9), 111; https://doi.org/10.3390/cryst6090111 - 8 Sep 2016
Cited by 4 | Viewed by 4350
Abstract
We numerically investigate the electromagnetic field localization in a two-dimensional photonic quasicrystal generated with a holographic tiling. We demonstrate that light confinement can be induced into an air mirrorless cavity by the inherent symmetry of the spatial distribution of the dielectric scatterers forming [...] Read more.
We numerically investigate the electromagnetic field localization in a two-dimensional photonic quasicrystal generated with a holographic tiling. We demonstrate that light confinement can be induced into an air mirrorless cavity by the inherent symmetry of the spatial distribution of the dielectric scatterers forming the side walls of the open cavity. Furthermore, the propagation direction can be controlled by suitable designs of the structure. This opens up new avenues for designing photonic materials and devices. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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<p>(<b>a</b>) Holographic-tiling binary irradiance: black points correspond to high intensity levels; the inset shows the Fourier diffraction spectrum of the pattern with pseudo-octagonal symmetry. (<b>b</b>) 2<span class="html-italic">D</span> Photonic Quasicrystal (PQC) finite pattern: open black circles correspond to the higher index pillars with <math display="inline"> <semantics> <mrow> <mi>r</mi> <mo>=</mo> <mn>240</mn> </mrow> </semantics> </math> nm; the positions of the sources and field monitors is indicated in the scheme (please note that monitors in different positions along the pattern detect different propagation direction of scattered field). (<b>c</b>) Same as in (b) for a structure in which an air channel is open along the vertical <span class="html-italic">y</span>-axis; extended monitors are used for integral power measurements. (<b>d</b>,<b>e</b>) local density of states (LDOS) of the finite holographic tiling (HT)-PQC for excitation pulse in different positions (red and grey source) in accordance with the scheme in (b). The spectra were calculated from several field monitors: the line color corresponds to the field monitor color depicted in (b) (red open circle monitors are not shown:); in (e), a different spectral range is used to better visualize the defect-free localized mode (DFLM) resonances in the wide PBG around 2.8 <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math>m. (<b>f</b>) LDOS for the channel-PQC pattern shown in (c) for low refractive index. The star indicates a representative resonance (2.01 <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math>m, DFLM) at which light propagation is forbidden above the symmetry center <span class="html-italic">x</span> = 0, <span class="html-italic">y</span> = 0 along the channel (crossed lines are a guide to the eye). The spectra line colors correspond to the field monitor colors in (c).</p>
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<p>(<b>a</b>) Contour map of the normalized field amplitude <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>z</mi> </msub> </semantics> </math> at the DFLM wavelength of 2.01 <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math>m in the channel-PQC (<math display="inline"> <semantics> <mrow> <mi mathvariant="normal">Δ</mi> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>): light cannot efficiently cross the pattern center. (<b>b</b>) Normalized contour map of <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>z</mi> </msub> </semantics> </math> at 2.01 <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math>m in the channel-PQC with a central pillar (<math display="inline"> <semantics> <mrow> <mi mathvariant="normal">Δ</mi> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>): light couples efficiently to the top half channel thanks to the central pillar. The field around the source is due to the sum of input and back-scattering fields, and takes into account also back-scattering from the pillars around the channel (due to the source injection).</p>
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<p>(<b>a</b>) Contour map of the normalized field amplitude <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>z</mi> </msub> </semantics> </math> at the DFLM wavelength of 2.01 <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math>m in the doubled channel-PQC (<math display="inline"> <semantics> <mrow> <mi mathvariant="normal">Δ</mi> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>): light cannot efficiently cross the top and bottom DFLMs, respectively at coordinates (<math display="inline"> <semantics> <mrow> <mi>x</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>) and (<math display="inline"> <semantics> <mrow> <mi>x</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>=</mo> <mo>−</mo> <mi>L</mi> </mrow> </semantics> </math>), acting as virtual mirrors that confine the electromagnetic field inside a mirrorless cavity. (<b>b</b>) Power monitored by the detectors placed as represented in the scheme in (a). The color of the solid lines corresponds to the field monitor colors in (a), i.e., blue for the input power, red for top transmitted power (T), yellow for the bottom transmitted power (B) and green for power detected just above the top virtual mirror (<math display="inline"> <semantics> <mrow> <mi>x</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>y</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math>). The field reaches a steady state with only ∼ 10% of loss through the open waveguide despite the relative low refractive index contrast of the photonic PQC. The input field has unitary power. The blue line indicates total power integrated in the blue-box area around the center where input source is launched.</p>
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<p>(<b>a</b>) Contour map of <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>z</mi> </msub> </semantics> </math> at the DFLM wavelength of 2.01<span class="html-italic">μ</span>m in the three-port channel-PQC (<math display="inline"> <semantics> <mrow> <mi mathvariant="normal">Δ</mi> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>). (<b>b</b>) Contour map of <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>z</mi> </msub> </semantics> </math> at the DFLM wavelength of 2.01<span class="html-italic">μ</span>m in the four-port channel-PQC (<math display="inline"> <semantics> <mrow> <mi mathvariant="normal">Δ</mi> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>8</mn> </mrow> </semantics> </math>).</p>
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4266 KiB  
Article
Molecular Structure, Spectroscopic and DFT Computational Studies of Arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione
by Assem Barakat, Saied M. Soliman, Hazem A. Ghabbour, M. Ali, Abdullah Mohammed Al-Majid, Mohammad Shahidul Islam and Ayman A. Ghfar
Crystals 2016, 6(9), 110; https://doi.org/10.3390/cryst6090110 - 8 Sep 2016
Cited by 3 | Viewed by 4379
Abstract
Reaction of barbituric acid derivatives and di-substituted benzaldehyde in water afforded arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione derivatives (1 and 2). The one step reaction proceeded efficiently, smoothly, and in excellent yield. The arylidene compounds were characterized by spectrophotometric tools [...] Read more.
Reaction of barbituric acid derivatives and di-substituted benzaldehyde in water afforded arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione derivatives (1 and 2). The one step reaction proceeded efficiently, smoothly, and in excellent yield. The arylidene compounds were characterized by spectrophotometric tools plus X-ray single crystal diffraction technique. Quantum chemical calculations were performed using the DFT/B3LYP method to optimize the structure of the two isomers (1 and 2) in the gas phase. The optimized structures were found to agree well with the experimental X-ray structure data. The highest occupied (HOMO) and lowest unoccupied (LUMO) frontier molecular orbitals analyses were performed and the atomic charges were calculated using natural populationanalysis. Full article
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<p>ORTEP (Oak Ridge Thermal-Ellipsoid Plot Program) of the synthesized compound <b>1</b> (<b>left</b>) and <b>2</b> (<b>right</b>). Displacement ellipsoids are plotted at the 40% probability level for non-H atoms.</p>
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<p>View of the molecular packing in compounds <b>1</b> and <b>2</b> The O–H<b><sup>…</sup></b>O and C–H<b><sup>…</sup></b>O hydrogen bonds are shown as dashed lines.</p>
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<p>The optimized structures (<b>left</b>) and comparative overlay of the calculated and experimental structure (<b>right</b>). Bond distance values are given in Å.</p>
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<p>The frontier molecular orbitals of the studied isomers.</p>
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<p>The natural charges at the different atomic sites of compounds <b>1</b> and <b>2</b>.</p>
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<p>Electrostatic potential (ESP) maps of <b>1</b> and <b>2</b>.</p>
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<p>Synthesis of arylidene-1,3-dimethylpyrimidine-2,4,6(1<span class="html-italic">H</span>,3<span class="html-italic">H</span>,5<span class="html-italic">H</span>)-trione derivatives <b>1</b> and <b>2</b>.</p>
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2526 KiB  
Article
Synthesis, Crystal Structure, and Cytotoxic Activity of a Novel Eight-Coordinated Dinuclear Ca(II)-Schiff Base Complex
by Xi-Shi Tai, Qing-Guo Meng and Li-Li Liu
Crystals 2016, 6(9), 109; https://doi.org/10.3390/cryst6090109 - 7 Sep 2016
Cited by 9 | Viewed by 3983
Abstract
A novel eight-coordinated dinuclear Ca(II) complex, [Ca2(L)2(H2O)10]·H2O (L = 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone) (1), was synthesized by the reaction of 3-pyridinecarboxylic hydrazide, disodium 4-formylbenzene-1,3-disulfonate, and Ca(ClO4)2·4H2O in [...] Read more.
A novel eight-coordinated dinuclear Ca(II) complex, [Ca2(L)2(H2O)10]·H2O (L = 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone) (1), was synthesized by the reaction of 3-pyridinecarboxylic hydrazide, disodium 4-formylbenzene-1,3-disulfonate, and Ca(ClO4)2·4H2O in ethanol-water solution (v:v = 3:1) at 50 °C. Complex 1 was characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and X-ray single crystal diffraction analysis. Dinuclear Ca(II) complex 1 belongs to triclinic, space group P-1 with a = 7.186(3) Å, b = 11.978(5) Å, c = 12.263(5) Å, α = 90.318(5)°, β = 91.922(5)°, γ = 96.797(5)°, V = 1047.5(8) Å3, Z = 1, Dc = 1.685 mg·m−3, μ = 0.572 mm−1, F(000) = 552, and final R1 = 0.0308, ωR2 = 0.0770. Dinuclear Ca(II) molecules form a 1D chained structure by π–π stacking interaction. The 1D chains form a 3D framework structure by the π–π stacking interaction and hydrogen bonds. The in vitro cytotoxic activity activity of 1 against HL-60 and MLTC-1 was also investigated. Full article
(This article belongs to the Section Biomolecular Crystals)
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<p>The IR spectrum of <b>1</b>.</p>
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<p>The coordination environment of <b>1</b>.</p>
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<p>1D chained structure of <b>1</b>.</p>
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<p>3D network structure of <b>1</b>.</p>
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4164 KiB  
Article
Crystallography of Representative MOFs Based on Pillared Cyanonickelate (PICNIC) Architecture
by Winnie Wong-Ng, Jeffrey T. Culp and Yu-Sheng Chen
Crystals 2016, 6(9), 108; https://doi.org/10.3390/cryst6090108 - 5 Sep 2016
Cited by 8 | Viewed by 6676
Abstract
The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be [...] Read more.
The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be especially diverse where pore size and pore functionality can be varied by the choice of pillar organic ligand. In addition, a number of PICNICs form soft porous structures that show reversible structure transitions during the adsorption and desorption of guests. The structural flexibility in these materials can be affected by relatively minor differences in ligand design, and the physical driving force for variations in host-guest behavior in these materials is still not known. One key to understanding this diversity is a detailed investigation of the crystal structures of both rigid and flexible PICNIC derivatives. This article gives a brief review of flexible MOFs. It also reports the crystal structures of five PICNICS from our laboratories including three 3-D porous frameworks (Ni-Bpene, NI-BpyMe, Ni-BpyNH2), one 2-D layer (Ni-Bpy), and one 1-D chain (Ni-Naph) compound. The sorption data of BpyMe for CO2, CH4 and N2 is described. The important role of NH3 (from the solvent of crystallization) as blocking ligands which prevent the polymerization of the 1-D chains and 2-D layers to become 3D porous frameworks in the Ni-Bpy and Ni-Naph compounds is also addressed. Full article
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<p>Schematic drawing demonstrating the opening/collapsing (decreasing/increasing the angle between the basal plane and the ligand) of the unit cells of Ni(L)[Ni(CN)<sub>4</sub>] in the presence of CO<sub>2</sub>.</p>
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<p>Tetracyano-nickelate square planar complex showing two different types of Nis (different coordination environment).</p>
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<p>Schematics of the pillar ligands with different lengths.</p>
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<p>Comparing typical gas adsorption (blue)-desorption (red) cycles for a rigid porous material (<b>top</b>) and a flexible MOF (<b>bottom</b>). Adsorption in flexible sorbents is associated with a gate-opening effect at a specific threshold condition of temperature and pressure. Desorption is hysteretic.</p>
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<p>Schematic drawing of the chemical formulas for the five pillar ligands: Naph, C<sub>8</sub>N<sub>2</sub>H<sub>6</sub>; Bpy, C<sub>10</sub>N<sub>2</sub>H<sub>8</sub>; BpyNH2, C<sub>10</sub>N<sub>3</sub>H<sub>9</sub>; BpyMe, C<sub>11</sub>N<sub>2</sub>H<sub>10</sub>; and Bpene, C<sub>12</sub>N<sub>2</sub>H<sub>10</sub>.</p>
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<p>The basic motif of Ni-Bpene (C-grey, N-blue, Ni-green; probability ellipsoids drawn at 50%).</p>
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<p>The 2-D tetracyanonickelate square grid network in Ni-Bpene (C-grey, N-blue, Ni-green).</p>
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<p>The Bpene ligands bridge the 2-D Ni[Ni(CN)<sub>4</sub>] sheets to form the 3-D pillared-layered structure (C-grey, N-blue, Ni-green).</p>
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<p>The basic motif of the Ni(BpyMe)[Ni(CN)<sub>4</sub>] molecules (C-grey, N-blue, Ni-green; probability ellipsoids drawn at 50%).</p>
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<p>Structure of Ni-BpyMe with disordered DMSO solvent inside the rectangular cage (view along the b-axis; C-grey, N-blue, Ni-green, S-yellow, O-red).</p>
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<p>Comparing CO<sub>2</sub> adsorption data at 30 °C for Ni-BpyMe powder (black) and single-crystal (red) samples. Plot (<b>b</b>) is shown to contrast the adsorption (solid)–desorption (open) behavior for CO<sub>2</sub> at 30 °C on the flexible PICNIC Ni-Bpene to that of the rigid Ni-BpyMe sample, plot (<b>a</b>).</p>
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<p>Adsorption data for CO<sub>2</sub> (diamonds), CH<sub>4</sub> (circles) and N<sub>2</sub> (triangles) at 40 °C (<b>a</b>) and at 20 °C on a crystalline sample of Ni-BpyMe (<b>b</b>).</p>
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<p>The basic motif of the Ni(BpyNH2)[Ni(CN)<sub>4</sub>] molecules (C-grey, N-blue, Ni-green; probability ellipsoids drawn at 50%).</p>
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<p>2-D Ni(CN)<sub>4</sub> wavy net connecting to each other via the Ni-BPyNH2 ligands to form a 3-D structure (C-grey, N-blue, Ni-green), viewing along <span class="html-italic">a</span>-axis.</p>
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<p>Ni-BPyNH2 square net view down the <span class="html-italic">b</span>-axis of the molecule (C-grey, N-blue, Ni-green).</p>
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<p>The basic motif of the Ni(Bpy)[Ni(CN)<sub>4</sub>] molecules (C-grey, N-blue, Ni-green; probability ellipsoids drawn at 50%).</p>
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<p>2-D structure of Ni-Bpy along <span class="html-italic">a</span>-axis, with sheet-like structure spreading in the <span class="html-italic">bc</span> direction (C-grey, N-blue, Ni-green).</p>
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<p>2-D sheets in Ni-Bpy are connected to each other via van der Waal’s forces and hydrogen bonding (view along <span class="html-italic">b</span>-axis; C-grey, N-blue, Ni-green).</p>
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<p>Terminal C≡N groups of the neighboring Ni-C-N-Ni-N-C-Ni chains in the Ni-Bpy structure forming a zigzag fashion (view along <span class="html-italic">c</span>-axis; C-grey, N-blue, Ni-green). The red broken lines indicate H-bonding.</p>
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<p>The basic motif of the Ni(Naph)[Ni(CN)<sub>4</sub>] molecules (C-grey, N-blue, Ni-green; probability ellipsoids drawn at 50%).</p>
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<p>The Ni-Naph structure showing 1-D chains of Ni(Naph)(NH<sub>3</sub>)<sub>4</sub> and individual units of planar [Ni(CN)<sub>4</sub>] groups (view along <span class="html-italic">b</span>-axis; C-grey, N-blue, Ni-green).</p>
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<p>TGA scan in air for crystals of Ni-BpyMe after extracting DMSO guests with methanol. All methanol guests are lost below 100 °C with no further weight loss prior to decomposition. The “expected” value on the plot is the expected ratio of the mass of residual NiO to mass of the guest-free framework as determined from the structure determined by single-crystal X-ray diffraction, whereas the “actual” ratio is the experimentally determined value taken at the indicated points in the scan. See Experimental Section for an explanation of how the ratio is calculated.</p>
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<p>TGA scan in air for neat clean crystals of Ni-BpyNH2. Loss of guest DMSO is complete by 250 °C yielding the guest-free framework. The “expected” value on the plot is the expected ratio of the mass of residual NiO to the mass of the guest-free framework as determined from the structure determined by single-crystal X-ray diffraction, whereas the “actual” ratio is the experimentally determined value taken at the indicated points in the scan. See Experimental Section for an explanation of how the ratio is calculated.</p>
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<p>TGA scan in air for neat crystals of Ni-Bpy. Loss of coordinated NH<sub>3</sub> occurs over the temperature range of 200 °C to 300 °C. The “expected” value on the plot is the expected ratio of the mass of residual NiO to the mass of the framework as determined from the structure determined by single-crystal X-ray diffraction, whereas the “actual” ratio is the experimentally determined value taken at the indicated points in the scan. See Experimental Section for an explanation of how the ratio is calculated.</p>
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<p>TGA scan in air for neat crystals of Ni-Naph. Loss of NH<sub>3</sub> occurs in two steps out to 300 °C followed by immediate decomposition of the material. (The initial small weight loss at low temperature may also indicate some impurity in the bulk sample as discussed in the main text.) The “expected” value on the plot is the expected ratio of the mass of residual NiO to the mass of the framework as determined from the structure determined by single-crystal X-ray diffraction, whereas the “actual” ratio is the experimentally determined value taken at the indicated points in the scan. See Experimental Section for an explanation of how the ratio is calculated.</p>
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4410 KiB  
Article
A Novel Effect of CO2 Laser Induced Piezoelectricity in Ag2Ga2SiS6 Chalcogenide Crystals
by Oleg V. Parasyuk, Galyna L. Myronchuk, Anatolij O. Fedorchuk, Ahmed M. El-Naggar, Abdullah Albassam, Andrii S. Krymus and Iwan V. Kityk
Crystals 2016, 6(9), 107; https://doi.org/10.3390/cryst6090107 - 31 Aug 2016
Cited by 6 | Viewed by 4338
Abstract
We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag2Ga2SiS6 single crystals. The piezoelectric studies were done under the influence of a CO2 laser (wavelength 10.6 μm, time [...] Read more.
We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag2Ga2SiS6 single crystals. The piezoelectric studies were done under the influence of a CO2 laser (wavelength 10.6 μm, time duration 200 ns, lasers with power densities varying up to 700 MW/cm2). Contrary to the earlier studies where the photoinduced piezoelectricity was done under the influence of the near IR lasers, the effect is higher by at least one order, which is a consequence of the phonon anharmonic contributions and photopolarizations. Such a discovery allows one to build infrared piezotronic devices, which may be used for the production of the IR laser tunable optoelectronic triggers and memories. This is additionally confirmed by the fact that analogous photoillumination by the near IR laser (Nd:YAG (1064 nm) and Er:glass laser (1540 nm)) gives the obtained values of the effective piezoelectricity at of least one order less. The effect is completely reversible with a relaxation time up to several milliseconds. In order to clarify the role of free carriers, additional studies of photoelectrical spectra were done. Full article
(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)
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<p>General view of the IR spectra.</p>
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<p>The second coordination for S atoms and the nearest coordination for cation atoms for (<b>a</b>) AgGaS<sub>2</sub>; (<b>b</b>) Ag<sub>2</sub>Ga<sub>2</sub>SiS<sub>6</sub> and (<b>c</b>) SiS<sub>2</sub>.</p>
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<p>The architecture of sulfur tetrahedra surrounding p-elements for compounds (<b>a</b>) AgGaS<sub>2</sub>; (<b>b</b>) Ag<sub>2</sub>Ga<sub>2</sub>SiS<sub>6</sub> and (<b>c</b>) SiS<sub>2</sub>.</p>
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<p>Space contour plot of the photoinduced piezoelectricity in the case of the CO<sub>2</sub> (<b>a</b>) and Nd:YAG (<b>b</b>) laser treatment. The white color corresponds to the surface points, without the piezoelectricity changes (0% changes). The black color corresponds to the maximal changes of the piezoelectricity (100% in the figure). The other colors corresponds to intermediate piezoelectricity. The specificity of the experiment allows one also to perform the evaluations of the piezoelectricity distribution in space.</p>
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<p>Occurrence of the grating diffraction in the crossed polarizers for the 1150-nm He-Ne laser probing beam during excitations by bicolor CO<sub>2</sub> pulsed lasers at a power of about 500 MW/cm<sup>2</sup>. Different colors correspond to different phase shifts in the gratings.</p>
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<p>Dependences of the piezoelectric coefficients versus the bicolor illumination by bicolor laser beams of different lasers. The results are presented for the optimal angles between the two photoinduced laser beams. CO<sub>2</sub> corresponds to the fundamental photoinduced laser wavelength of 10.6 μm; CO, 5.5 μm; Er:glass, 1540 nm; YAG:Nd, 1064 nm.</p>
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<p>Changes of the photoinduced birefringence effect at a photoinduced illumination of 500 MW/cm<sup>2</sup> at an angle of 30° (<b>a</b>) and at a photoinduced power of about 500 MW/cm<sup>2</sup> at an incident angle of 24° (<b>b</b>).</p>
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<p>Control of the photoinduced birefringence profile in the direction of the photoinduced light propagation at 1150 nm for two CO<sub>2</sub> laser beam power densities: (<b>a</b>) 200 MW/cm<sup>2</sup>; (<b>b</b>) 500 MW/cm<sup>2</sup>.</p>
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<p>Spectral distribution of the photoconductivity for Ag<sub>2</sub>Ga<sub>2</sub>SiS<sub>6</sub>.</p>
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<p>(<b>a</b>) Photoconductivity relaxations during rectangular pulse excitations of different powers; (<b>b</b>) dependence of the stationary carrier concentration of the non-equilibrium carriers versus the light intensity.</p>
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1391 KiB  
Communication
Packing of Helices: Is Chirality the Highest Crystallographic Symmetry?
by Romain Gautier and Kenneth R. Poeppelmeier
Crystals 2016, 6(9), 106; https://doi.org/10.3390/cryst6090106 - 30 Aug 2016
Cited by 8 | Viewed by 6977
Abstract
Chiral structures resulting from the packing of helices are common in biological and synthetic materials. Herein, we analyze the noncentrosymmetry (NCS) in such systems using crystallographic considerations. A comparison of the chiral structures built from helices shows that the chirality can be expected [...] Read more.
Chiral structures resulting from the packing of helices are common in biological and synthetic materials. Herein, we analyze the noncentrosymmetry (NCS) in such systems using crystallographic considerations. A comparison of the chiral structures built from helices shows that the chirality can be expected for specific building units such as 31/32 or 61/65 helices which, in hexagonal arrangement, will more likely lead to a chiral resolution. In these two systems, we show that the highest crystallographic symmetry (i.e., the symmetry which can describe the crystal structure from the smallest assymetric unit) is chiral. As an illustration, we present the synthesis of two materials ([Zn(2,2’-bpy)3](NbF6)2 and [Zn(2,2’-bpy)3](TaF6)2) in which the 3n helices pack into a chiral structure. Full article
(This article belongs to the Special Issue Nonlinear Optical Crystals)
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<p>Representation of examples of packings for (<b>a</b>) a chiral assembly of 3<sub>n</sub> helices in hexagonal arrangement, (<b>b</b>) a chiral assembly of 6<sub>n</sub> helices in hexagonal arrangement, (<b>c</b>) a chiral assembly of 4<sub>n</sub> helices in tetragonal arrangement, (<b>d</b>) a non-chiral assembly of 4<sub>n</sub> helices in tetragonal arrangement. The red arrows and black triangles represent the handedness of helices and the helicates, respectively. In order to be symmetrically equivalent, the helicates must have the same environment.</p>
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<p>List of space groups exhibiting (<b>a</b>) 3<sub>n</sub> screw axes in hexagonal arrangement, (<b>b</b>) 6<sub>n</sub> screw axes in hexagonal arrangement and, (<b>c</b>) 4<sub>n</sub> screw axes in tetragonal arrangement. Space groups in red color are chiral. Space groups in bold are polar. No space groups combining 3<sub>1</sub> and 3<sub>2</sub> screw axes or 6<sub>1</sub> and 6<sub>5</sub> screw axes exist.</p>
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<p>View of (<b>a</b>) the two enantiomers <span class="html-italic">Δ</span> and <span class="html-italic">Λ</span>-[Zn(2,2’-bipy)<sub>3</sub>]<sup>2+</sup>, along the three-fold rotation axes, and (<b>b</b>) the two enantiomorphic 3<sub>1</sub> and 3<sub>2</sub> helices built from <span class="html-italic">Δ</span> and <span class="html-italic">Λ</span>-[Zn(2,2’-bipy)<sub>3</sub>]<sup>2+</sup>, respectively; π-stacking occurs between [Zn(2,2’-bipy)<sub>3</sub>]<sup>2+</sup> helicates.</p>
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4002 KiB  
Review
A Review of Transmission Electron Microscopy of Quasicrystals—How Are Atoms Arranged?
by Ruitao Li, Zhong Li, Zhili Dong and Khiam Aik Khor
Crystals 2016, 6(9), 105; https://doi.org/10.3390/cryst6090105 - 26 Aug 2016
Cited by 17 | Viewed by 11115
Abstract
Quasicrystals (QCs) possess rotational symmetries forbidden in the conventional crystallography and lack translational symmetries. Their atoms are arranged in an ordered but non-periodic way. Transmission electron microscopy (TEM) was the right tool to discover such exotic materials and has always been a main [...] Read more.
Quasicrystals (QCs) possess rotational symmetries forbidden in the conventional crystallography and lack translational symmetries. Their atoms are arranged in an ordered but non-periodic way. Transmission electron microscopy (TEM) was the right tool to discover such exotic materials and has always been a main technique in their studies since then. It provides the morphological and crystallographic information and images of real atomic arrangements of QCs. In this review, we summarized the achievements of the study of QCs using TEM, providing intriguing structural details of QCs unveiled by TEM analyses. The main findings on the symmetry, local atomic arrangement and chemical order of QCs are illustrated. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Figure 1
<p>Icosahedral structure: SAED patterns taken along (<b>a</b>) 5-fold symmetry axis; (<b>b</b>) 3-fold symmetry axis and (<b>c</b>) 2-fold symmetry axis; (<b>d</b>) three types of symmetry axes in the icosahedral structure; (<b>e</b>) stereographic projection of the symmetry elements of the icosahedral group ((<b>a</b>–<b>e</b>) reproduced from reference [<a href="#B1-crystals-06-00105" class="html-bibr">1</a>] with permission).</p>
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<p>Decagonal structure: (<b>a</b>) schematic of decagonal structure; SAED patterns taken along (<b>b</b>) 10-fold symmetry axis, (<b>c</b>) 2-fold symmetry axis A and (<b>d</b>) 2-fold symmetry axis B of Al<sub>70</sub>Ni<sub>20</sub>Rh<sub>10</sub> (reproduced from reference [<a href="#B31-crystals-06-00105" class="html-bibr">31</a>] with permission).</p>
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<p>A quarter of SAED pattern of different decagonal Al–Co–Ni structures: (<b>a</b>) Ni-rich basic structure; (<b>b</b>) S1-type; (<b>c</b>) Type-I; (<b>d</b>) Type-II; (<b>e</b>) transition state between types I and II; and (<b>f</b>) type I superstructure of five-fold QC (reproduced from reference [<a href="#B57-crystals-06-00105" class="html-bibr">57</a>] with permission).</p>
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<p>CBED patterns taken along the periodic axis of decagonal QCs: (<b>a</b>) Al<sub>70</sub>Cu<sub>4</sub>Co<sub>26</sub> (P<math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mn>10</mn> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math>m2) and (<b>b</b>) Al<sub>70</sub>Ni<sub>20</sub>Rh<sub>10</sub> (P10<sub>5</sub>/mmc) (reproduced from reference [<a href="#B75-crystals-06-00105" class="html-bibr">75</a>] and reference [<a href="#B31-crystals-06-00105" class="html-bibr">31</a>], respectively, with permission).</p>
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<p>HRTEM image taken along the 5-fold axis of icosahedral Al–Cu–Fe: (<b>a</b>) aperiodic but ordered distribution of bright dots; (<b>b</b>) enlargement of (<b>a</b>). The five arrows in (<b>a</b>) show that bright dots are lying along 5-fold symmetry directions; the pentagons in (<b>b</b>) indicate that bright dots can form pentagons of different sizes (reproduced from reference [<a href="#B33-crystals-06-00105" class="html-bibr">33</a>] with permission. Copyright 1988 The Japan Society of Applied Physics).</p>
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<p>HRTEM images of decagonal Al<sub>72</sub>Ni<sub>20</sub>Co<sub>8</sub> with the background subtracted: (<b>a</b>) Gummelt tiling; (<b>b</b>) a representative decagonal cluster; and (<b>c</b>) the comparison between the mirror-symmetry model and the rectangular region in (<b>b</b>) (reproduced from reference [<a href="#B91-crystals-06-00105" class="html-bibr">91</a>] with permission).</p>
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<p>Models of decagonal clusters with three different symmetries (red dots indicate Al atoms, black dots transitional atoms. Reproduced from reference [<a href="#B95-crystals-06-00105" class="html-bibr">95</a>] with permission).</p>
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<p>Ultrahigh-resolution HAADF-STEM images of decagonal Al<sub>64</sub>Cu<sub>22</sub>Co<sub>14</sub> taken along the periodic axis: (<b>a</b>) original image; and (<b>b</b>) image after maximum-entropy deconvolution (reproduced from reference [<a href="#B46-crystals-06-00105" class="html-bibr">46</a>] with permission).</p>
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3198 KiB  
Review
Statistical Approach to Diffraction of Periodic and Non-Periodic Crystals—Review
by Radoslaw Strzalka, Ireneusz Buganski and Janusz Wolny
Crystals 2016, 6(9), 104; https://doi.org/10.3390/cryst6090104 - 26 Aug 2016
Cited by 15 | Viewed by 5099
Abstract
In this paper, we show the fundamentals of statistical method of structure analysis. Basic concept of a method is the average unit cell, which is a probability distribution of atomic positions with respect to some reference lattices. The distribution carries complete structural information [...] Read more.
In this paper, we show the fundamentals of statistical method of structure analysis. Basic concept of a method is the average unit cell, which is a probability distribution of atomic positions with respect to some reference lattices. The distribution carries complete structural information required for structure determination via diffraction experiment regardless of the inner symmetry of diffracting medium. The shape of envelope function that connects all diffraction maxima can be derived as the Fourier transform of a distribution function. Moreover, distributions are sensitive to any disorder introduced to ideal structure—phonons and phasons. The latter are particularly important in case of quasicrystals. The statistical method deals very well with phason flips and may be used to redefine phasonic Debye-Waller correction factor. The statistical approach can be also successfully applied to the peak’s profile interpretation. It will be shown that the average unit cell can be equally well applied to a description of Bragg peaks as well as other components of diffraction pattern, namely continuous and singular continuous components. Calculations performed within statistical method are equivalent to the ones from multidimensional analysis. The atomic surface, also called occupation domain, which is the basic concept behind multidimensional models, acquires physical interpretation if compared to average unit cell. The statistical method applied to diffraction analysis is now a complete theory, which deals equally well with periodic and non-periodic crystals, including quasicrystals. The method easily meets also any structural disorder. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Figure 1
<p>A construction of the average unit cell for two reference lattices (black vertical bars) with lattice constants <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mi>k</mi> </msub> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mi>q</mi> </msub> </mrow> </semantics> </math>. Grey atoms of an arbitrary crystal structure (here the nodes of 1D Fibonacci chain) are projected on reference lattices (red and blue crosses). Distances to the nearest nodes are marked with <math display="inline"> <semantics> <mi>u</mi> </semantics> </math> and <math display="inline"> <semantics> <mi>v</mi> </semantics> </math>.</p>
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<p>(<b>a</b>) Distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mrow> <mi>u</mi> <mo>,</mo> <mi>v</mi> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>, marginal distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> and scaling relation <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mo>−</mo> <msup> <mi>τ</mi> <mn>2</mn> </msup> <mi>u</mi> </mrow> </semantics> </math> for the Fibonacci chain. It is shown that <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mrow> <mi>u</mi> <mo>,</mo> <mi>v</mi> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> is non-zero only along <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> line. (<b>b</b>) Distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> and (<b>c</b>) scaling <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>for harmonically modulated structure with single modulation term (<math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>=</mo> <mn>0.2</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>=</mo> <mn>1.0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>ξ</mi> <mo>=</mo> <mi>τ</mi> </mrow> </semantics> </math>). (<b>d</b>) AUC for the Thue-Morse sequence with probabilities of two characteristic positions <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </semantics> </math> in the chain. Reference lattice parameter <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mi>k</mi> </msub> <mo>=</mo> <mi>a</mi> <mo>+</mo> <mi>b</mi> </mrow> </semantics> </math>.</p>
Full article ">Figure 2 Cont.
<p>(<b>a</b>) Distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mrow> <mi>u</mi> <mo>,</mo> <mi>v</mi> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>, marginal distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> and scaling relation <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mo>−</mo> <msup> <mi>τ</mi> <mn>2</mn> </msup> <mi>u</mi> </mrow> </semantics> </math> for the Fibonacci chain. It is shown that <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mrow> <mi>u</mi> <mo>,</mo> <mi>v</mi> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> is non-zero only along <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> line. (<b>b</b>) Distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> and (<b>c</b>) scaling <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>for harmonically modulated structure with single modulation term (<math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>=</mo> <mn>0.2</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>=</mo> <mn>1.0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>ξ</mi> <mo>=</mo> <mi>τ</mi> </mrow> </semantics> </math>). (<b>d</b>) AUC for the Thue-Morse sequence with probabilities of two characteristic positions <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </semantics> </math> in the chain. Reference lattice parameter <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mi>k</mi> </msub> <mo>=</mo> <mi>a</mi> <mo>+</mo> <mi>b</mi> </mrow> </semantics> </math>.</p>
Full article ">Figure 3
<p>(<b>a</b>) Structure factor <math display="inline"> <semantics> <mrow> <mi>F</mi> <mrow> <mo stretchy="false">(</mo> <mi>k</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> calculated for the Fibonacci chain using formula (11) with first 4 envelopes <math display="inline"> <semantics> <mrow> <mi>m</mi> <mo>=</mo> <mrow> <mo stretchy="false">{</mo> <mrow> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mn>3</mn> </mrow> <mo stretchy="false">}</mo> </mrow> </mrow> </semantics> </math> marked with different colors (red, olive, blue and cyan); (<b>b</b>) Diffraction pattern of the Fibonacci chain calculated as squared formula (11) with first 4 envelopes marked (notation from the left figure used). Peaks are distributed periodically within an envelope (period <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> <msup> <mi>τ</mi> <mn>2</mn> </msup> </mrow> <mrow> <msup> <mi>τ</mi> <mn>2</mn> </msup> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> <mo>≈</mo> <mn>4.54</mn> <mo> </mo> <mrow> <mo stretchy="false">[</mo> <mrow> <mi>a</mi> <mo>.</mo> <mi>u</mi> <mo>.</mo> </mrow> <mo stretchy="false">]</mo> </mrow> </mrow> </semantics> </math>) and envelopes are deployed with periodicity <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>1</mn> </msub> <mo>=</mo> <msqrt> <mn>5</mn> </msqrt> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>≈</mo> <mn>10.2</mn> <mo> </mo> <mrow> <mo stretchy="false">[</mo> <mrow> <mi>a</mi> <mo>.</mo> <mi>u</mi> <mo>.</mo> </mrow> <mo stretchy="false">]</mo> </mrow> </mrow> </semantics> </math> which is an incommensurate ratio relative to scaling factor <math display="inline"> <semantics> <mi>τ</mi> </semantics> </math>; (<b>c</b>) Exemplary diffraction pattern calculated using formula (13) along given direction in reciprocal space for the simple decoration of CdYb and AlPdMn icosahedral phase.</p>
Full article ">Figure 4
<p>(<b>a</b>) Structure factor <math display="inline"> <semantics> <mrow> <mi>F</mi> <mrow> <mo stretchy="false">(</mo> <mi>k</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> calculated using formula (14) and (<b>b</b>) Diffraction intensities <math display="inline"> <semantics> <mrow> <mi>I</mi> <mrow> <mo stretchy="false">(</mo> <mi>k</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> calculated as squared formula (14) for harmonically modulated structure with single modulation term (<math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>=</mo> <mn>0.2</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>=</mo> <mn>1.0</mn> </mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mi>ξ</mi> <mo>=</mo> <mi>τ</mi> </mrow> </semantics> </math>). Due to known property of Bessel functions, <math display="inline"> <semantics> <mrow> <msub> <mi>J</mi> <mrow> <mo>−</mo> <mi>m</mi> </mrow> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mo>−</mo> <msub> <mi>J</mi> <mi>m</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math>, the peaks presented in <math display="inline"> <semantics> <mrow> <mi>I</mi> <mrow> <mo stretchy="false">(</mo> <mi>k</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> plot are doubled. First 5 envelopes marked with different colors. (<b>c</b>) Diffraction pattern of the Thue-Morse sequence with Bragg component (envelope function calculated as squared formula (15) for <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <mrow> <mn>1.1</mn> </mrow> </mfrac> <mo>≈</mo> <mn>5.71</mn> <mo> </mo> <mrow> <mo stretchy="false">[</mo> <mrow> <mi>a</mi> <mo>.</mo> <mi>u</mi> <mo>.</mo> </mrow> <mo stretchy="false">]</mo> </mrow> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <mn>0.1</mn> </mrow> </semantics> </math>, marked with red) and singular continuous component. The full diffraction pattern (both components) <math display="inline"> <semantics> <mrow> <mi>I</mi> <mrow> <mo stretchy="false">(</mo> <mi>k</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> are plotted with black line.</p>
Full article ">Figure 5
<p>(<b>a</b>) The intensities of the multiple slit diffraction image calculated numerically for various number of scatterers (<math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mrow> <mo stretchy="false">{</mo> <mrow> <mn>2</mn> <mo>,</mo> <mn>3</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>10</mn> <mo>,</mo> <mn>100</mn> </mrow> <mo stretchy="false">}</mo> </mrow> </mrow> </semantics> </math>). The peaks get narrower with increasing <math display="inline"> <semantics> <mi>N</mi> </semantics> </math>. All peak heights are reduced to one. (<b>b</b>) Real picture of intensities calculated for three number of scatterers <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mrow> <mo stretchy="false">{</mo> <mrow> <mn>20</mn> <mo>,</mo> <mn>15</mn> <mo>,</mo> <mn>10</mn> </mrow> <mo stretchy="false">}</mo> </mrow> </mrow> </semantics> </math>. It is clearly seen that peak heights at <math display="inline"> <semantics> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> scale with <math display="inline"> <semantics> <mrow> <msup> <mi>N</mi> <mn>2</mn> </msup> </mrow> </semantics> </math>, whereas the scaling of intensities taken for different <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>1</mn> </msub> <mo>≠</mo> <msub> <mi>k</mi> <mn>0</mn> </msub> </mrow> </semantics> </math> (marked with different colors) is different. For both figures <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>2</mn> <mi>π</mi> </mrow> </semantics> </math> (in arbitrary units).</p>
Full article ">Figure 6
<p>Scaling of diffraction intensities plotted vs. coherence length (number of atoms in the chain). The significant deviation from <math display="inline"> <semantics> <mrow> <msup> <mi>N</mi> <mn>2</mn> </msup> </mrow> </semantics> </math> clearly seen even for small values <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>1</mn> </msub> </mrow> </semantics> </math> relative to <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>2</mn> <mi>π</mi> </mrow> </semantics> </math>.</p>
Full article ">Figure 7
<p>(<b>a</b>) The average unit cell <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> constructed for <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <mrow> <msub> <mi>k</mi> <mn>1</mn> </msub> </mrow> </mfrac> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0.95</mn> <mo> </mo> <msub> <mi>k</mi> <mn>0</mn> </msub> </mrow> </semantics> </math> (<math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>2</mn> <mi>π</mi> </mrow> </semantics> </math>), for two structures: (left) periodic chain of <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>15</mn> </mrow> </semantics> </math> point-like scatterers and (<b>b</b>) quasicrystal constructed with three distributions <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> (violet, olive and sky blue colors) of width <math display="inline"> <semantics> <mrow> <mfrac> <mn>1</mn> <mn>3</mn> </mfrac> <msub> <mi>λ</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>3</mn> </mfrac> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> </mrow> </mfrac> </mrow> </semantics> </math> each. Shapes of <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> strongly depend on the number of atoms <math display="inline"> <semantics> <mi>N</mi> </semantics> </math>.</p>
Full article ">Figure 8
<p>(<b>a</b>) Modified marginal distribution <math display="inline"> <semantics> <mrow> <mi>P</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> of the Fibonacci chain with phonons (original shape for ideal structure marked with dotted line); (<b>b</b>) TAU2-scaling relation for Fibonacci chain modified by Gaussian phononic smearing. Respective <math display="inline"> <semantics> <mrow> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>u</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </semantics> </math> relation for ideal structure shown in the inset. In both plots the amplitude of phonons was 2% of <math display="inline"> <semantics> <mrow> <msub> <mi>λ</mi> <mi>k</mi> </msub> </mrow> </semantics> </math>; (<b>c</b>) Envelope functions of the diffraction peaks for the Fibonacci chain with phononic disorder corrected by three different multiplicative correction functions: Gaussian (standard Debye-Waller factor black), Bessel (red) and cardinal sine (blue) plotted relative to intensities calculated for ideal structure with no phonons. Main scattering vector <math display="inline"> <semantics> <mrow> <msub> <mi>k</mi> <mn>0</mn> </msub> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> <mi>τ</mi> </mrow> <mrow> <msup> <mi>τ</mi> <mn>2</mn> </msup> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> <mo>≈</mo> <mn>2.81</mn> <mo> </mo> <mrow> <mo stretchy="false">[</mo> <mrow> <mi>a</mi> <mo>.</mo> <mi>u</mi> <mo>.</mo> </mrow> <mo stretchy="false">]</mo> </mrow> </mrow> </semantics> </math>.</p>
Full article ">Figure 9
<p>(<b>a</b>) AUC for the Fibonacci chain with phasons (flip ratio <math display="inline"> <semantics> <mrow> <mi>α</mi> <mo>=</mo> <mn>5</mn> <mo>%</mo> </mrow> </semantics> </math>). Red arrow show the move of the fragment originally placed within the AUC of ideal Fibonacci chain to a new position where there was zero-probability before; (<b>b</b>) Calculated vs. “observed” intensities in the diffraction diagram of Fibonacci chain with phasons (<math display="inline"> <semantics> <mrow> <mi>α</mi> <mo>=</mo> <mn>5</mn> <mo>%</mo> </mrow> </semantics> </math>) and standard phasonic Debye-Waller correction given by formula (18). The characteristic bias is observed for weak reflections (<math display="inline"> <semantics> <mrow> <mi>I</mi> <mo>&lt;</mo> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics> </math>); (<b>c</b>) The same figure as (b) but with correction given by formula (17) obtained by a statistical method. Perfect fit is observed with only small spread caused by numerical errors (finite size of sample, number of atoms of about <math display="inline"> <semantics> <mrow> <msup> <mn>10</mn> <mn>6</mn> </msup> </mrow> </semantics> </math>).</p>
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7470 KiB  
Article
Facet Appearance on the Lateral Face of Sapphire Single-Crystal Fibers during LHPG Growth
by Liudmila D. Iskhakova, Vitalii V. Kashin, Sergey V. Lavrishchev, Sergey Ya. Rusanov, Vladimir F. Seregin and Vladimir B. Tsvetkov
Crystals 2016, 6(9), 101; https://doi.org/10.3390/cryst6090101 - 25 Aug 2016
Cited by 6 | Viewed by 7545
Abstract
Results of the study of the lateral surface of single-crystal (SC) sapphire fibers grown along crystallographic directions [ 0001 ] and [ 11 2 ¯ 0 ] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface [...] Read more.
Results of the study of the lateral surface of single-crystal (SC) sapphire fibers grown along crystallographic directions [ 0001 ] and [ 11 2 ¯ 0 ] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface of the fibers depending on the growth direction is analyzed. The crystallographic orientation of the facets is investigated. The microstructure of the samples is investigated with the help of an optical microscope and a JSM-5910LV scanning electronic microscope (JEOL). The crystallographic orientations of the facets on the SC sapphire fiber surface are determined by electron backscatter diffraction (EBSD). The seed orientation is studied by means of XRD techniques. Full article
(This article belongs to the Special Issue Traveling Solvent Floating Zone (TSFZ) Method in Crystal Growth)
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<p>Schematic of experimental set-up. The pulling of the fiber is directed from the bottom upwards.</p>
Full article ">Figure 2
<p>Crystallographic diagram of sapphire.</p>
Full article ">Figure 3
<p>Determination of the seed orientation by means of the XRD techniques: (<b>a</b>) Positioning on X-ray beam on samples area by means laser-video system; (<b>b</b>) scan frame; (<b>c</b>) XRD pattern.</p>
Full article ">Figure 4
<p>Optical (<b>A</b>) and SEM photographs (<b>B</b>,<b>C</b>) of an SC sapphire fiber grown up along axis [0001] at the precise seed orientation. Photographs demonstrate a slightly rounded-off cross-section (<b>A</b>); the absence of large facets, but the presence of micro-facets on the lateral surface (<b>B</b>); and the period of the small-scale faceting of the lateral surface (<b>C</b>).</p>
Full article ">Figure 5
<p>Z-contrast SEM image (<b>A</b>,<b>B</b>) and optical photographs (<b>C</b>,<b>D</b>) of an SC sapphire fiber grown up along axis [0001] at different seed misalignment: Δα<sub>1</sub> ≈ 2.5° (<b>A</b>,<b>B</b>); Δα<sub>2</sub> ≈ 7° (<b>C</b>,<b>D</b>).</p>
Full article ">Figure 6
<p>SEM image of an SC sapphire fiber grown along axis [11<math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>2</mn> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math>0] (<b>A</b>) general view; (<b>B</b>) the view of one of the steps.</p>
Full article ">Figure 7
<p>Optical microphotograph (<b>A</b> bottom, <b>D</b>) and SEM image (<b>B</b>) of a sapphire SC fiber grown along axis [11<math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>2</mn> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math>0]: (<b>A</b>) general view of flat faces; (<b>B</b>) SEM image of one of the flat planes, with the region of the EBSD-measurement pointed out by a rectangle; (<b>C</b>) polar figure after JSM-5910LV (JEOL) software; (<b>D</b>) general view of the defected faces (combination of several photos along the sapphire fiber).</p>
Full article ">Figure 8
<p>SEM image of a sapphire SC fiber grown along axis [11<math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>2</mn> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math>0]: (<b>A</b>) general view of one of the facets (<span class="html-italic">r</span>-plane); (<b>B</b>) microstructure of the central part of the facet; (<b>C</b>) growth steps near the boundary of the flat face.</p>
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2579 KiB  
Article
Three-Dimensional Cadmium(II) Cyanide Coordination Polymers with Ethoxy-, Butoxy- and Hexyloxy-ethanol
by Takeshi Kawasaki and Takafumi Kitazawa
Crystals 2016, 6(9), 103; https://doi.org/10.3390/cryst6090103 - 24 Aug 2016
Cited by 2 | Viewed by 5759
Abstract
The three novel cadmium(II) cyanide coordination polymers with alkoxyethanols, [Cd(CN)2(C2H5OCH2CH2OH)]n (I), [{Cd(CN)2(C4H9OCH2CH2OH)}3{Cd(CN)2}]n (II) [...] Read more.
The three novel cadmium(II) cyanide coordination polymers with alkoxyethanols, [Cd(CN)2(C2H5OCH2CH2OH)]n (I), [{Cd(CN)2(C4H9OCH2CH2OH)}3{Cd(CN)2}]n (II) and [{Cd(CN)2(H2O)2}{Cd(CN)2}3·2(C6H13OCH2CH2OH)]n (III), were synthesized and charcterized by structural determination. Three complexes have three-dimensional Cd(CN)2 frameworks; I has distorted tridymite-like structure, and, II and III have zeolite-like structures. The cavities of Cd(CN)2 frameworks of the complexes are occupied by the alkoxyethanol molecules. In I and II, hydroxyl oxygen atoms of alkoxyethanol molecules coordinate to the Cd(II) ions, and the Cd(II) ions exhibit slightly distort trigonal-bipyramidal coordination geometry. In II, there is also tetrahedral Cd(II) ion which is coordinated by only the four cyanides. The hydroxyl oxygen atoms of alkoxyethanol connects etheric oxygen atoms of the neighboring alkoxyethanol by hydrogen bond in I and II. In III, hexyloxyethanol molecules do not coordinate to the Cd(II) ions, and two water molecules coordnate to the octahedral Cd(II) ions. The framework in III contains octahedral Cd(II) and tetrahedral Cd(II) in a 1:3 ratio. The Cd(CN)2 framework structures depended on the difference of alkyl chain for alkoxyethanol molecules. Full article
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Graphical abstract
Full article ">Figure 1
<p>Crystal structure of <b>I</b>. H atoms except OH hydrogens are omitted for clarity: (<b>a</b>) Asymmetric unit. Displacement ellipsoids are drawn at the 30% probability level. Because arrangements of cyanides (Cd–NC–Cd or Cd–CN–Cd) are disordered, the atoms of cyanide are labeled less clearly; (<b>b</b>) The Cd(CN)<sub>2</sub> network structure view along the <span class="html-italic">a</span> axis; (<b>c</b>) Hydrogen bonds between neighboring Etcel ligands in cavities of distorted-tridymite-like cadmium cyanide network of <b>I</b>. Displacement ellipsoids are drawn at the 30% probability level. The disorder part is omitted for clarity. (Symmetry codes: iv = −<span class="html-italic">x</span> + 1, <span class="html-italic">y</span>, −<span class="html-italic">z</span> + 3/2).</p>
Full article ">Figure 2
<p>Crystal structure of <b>II</b>. H atoms except OH hydrogens and disorder parts are omitted for clarity: (<b>a</b>) Asymmetric unit. Displacement ellipsoids are drawn at the 30% probability level. Because arrangements of cyanides (Cd–NC–Cd or Cd–CN–Cd) are disordered, the atoms of cyanide are labeled less clearly; (<b>b</b>) The Cd(CN)<sub>2</sub> network structure of the view along the <span class="html-italic">a</span> axis; (<b>c</b>) [6<sup>5</sup>] <b>t-afi</b>, [4<sup>2</sup>.6<sup>4</sup>] <b>t-lau</b> and [6<sup>2</sup>.8<sup>2</sup>] <b>t-kaa</b> tiles; (<b>d</b>) Hydrogen bonds between neighboring Bucel ligands in cavities of cadmium cyanide network of <b>II</b>. Displacement ellipsoids are drawn at the 30% probability level. (Symmetry codes: ii = −<span class="html-italic">x</span> + 1, <span class="html-italic">y</span> − 1/2, −<span class="html-italic">z</span> + 1/2; iv = −<span class="html-italic">x</span> + 1, −<span class="html-italic">y</span> + 1, −<span class="html-italic">z</span>).</p>
Full article ">Figure 3
<p>Crystal structure of <b>III</b>. H atoms and disorder parts are omitted for clarity: (<b>a</b>) Asymmetric unit of <b>III</b>. Displacement ellipsoids are drawn at the 30% probability level. Because arrangements of cyanides (Cd–NC–Cd or Cd–CN–Cd) are disordered, the atoms of cyanide are labeled less clearly; (<b>b</b>) The Cd(CN)<sub>2</sub> network structure of <b>III</b> along the <span class="html-italic">b</span> axis; (<b>c</b>) [6<sup>4</sup>] <b>t-hes</b> and [4<sup>2</sup>.6<sup>2</sup>.8<sup>2</sup>] <b>t-kdq</b> tiles; (<b>d</b>) Hydrogen bonds between Hexcel and water molecules in cavities of cadmium cyanide network. Displacement ellipsoids are drawn at the 30% probability level. (symmetry codes: iv = <span class="html-italic">x</span> + 1/2, <span class="html-italic">y</span>, −<span class="html-italic">z</span> + 3/2; vii = <span class="html-italic">x</span>, <span class="html-italic">y</span> −1, <span class="html-italic">z</span>; viii = −<span class="html-italic">x</span> + 1, −<span class="html-italic">y</span> + 1, −<span class="html-italic">z</span> + 1).</p>
Full article ">Scheme 1
<p>Structural formulae of alkoxyethanol compounds used in this work.</p>
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Article
The First Homoleptic Complex of Seven-Coordinated Osmium: Synthesis and Crystallographical Evidence of Pentagonal Bipyramidal Polyhedron of Heptacyanoosmate(IV)
by Eugenia V. Peresypkina, Anatolie Gavriluta and Kira E. Vostrikova
Crystals 2016, 6(9), 102; https://doi.org/10.3390/cryst6090102 - 23 Aug 2016
Cited by 5 | Viewed by 6683
Abstract
The ligand exchange in (n-Bu4N)2OsIVCl6 (n-Bu4N = tetra-n-butylammonium) leads to the formation of the osmium(IV) heptacyanide, the first fully inorganic homoleptic complex of heptacoordinated osmium. The single-crystal X-ray [...] Read more.
The ligand exchange in (n-Bu4N)2OsIVCl6 (n-Bu4N = tetra-n-butylammonium) leads to the formation of the osmium(IV) heptacyanide, the first fully inorganic homoleptic complex of heptacoordinated osmium. The single-crystal X-ray diffraction (SC-XRD) study reveals the pentagonal bipyramidal molecular structure of the [Os(CN)7]3− anion. The latter being a diamagnetic analogue of the highly anisotropic paramagnetic synthon, [ReIV(CN)7]3− can be used for the synthesis of the model heterometallic coordination compounds for the detailed study and simulation of the magnetic properties of the low-dimensional molecular nanomagnets involving 5d metal heptacyanides. Full article
(This article belongs to the Special Issue Crystal Structure of Complex Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Structure of pentagonal bipyramidal [Os(CN)<sub>7</sub>]<sup>3−</sup> complex in <b>1</b>.</p>
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<p>The numbering scheme in two independent molecules of the [Os(CN)<sub>7</sub>]<sup>3−</sup> complex.</p>
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<p>Calculated from the single-crystal diffraction data (red) and experimental powder XRD (black) diffractograms for <b>1</b>.</p>
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<p>The qualitative d-orbital energy-splitting diagram for pentagonal bipyramidal geometry and the ground-state electronic configuration of <b>1</b>.</p>
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