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    Crystal Structure-Types

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    Bhaskara P Achar
    The document discusses crystalline structure in engineering materials. Crystalline solids have particles (atoms, molecules, ions) arranged in a definite repetitive geometric pattern with like neighbors. This periodic arrangement can be described by a lattice consisting of points in space. Any point in the 3D lattice is defined by a position vector based on integer multiples of three unit vectors a, b, c. Repeating this unit cell generates the crystal structure. There are 7 crystal systems based on the length and orientation of the unit vectors.

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    Crystal Structure-Types

    Uploaded by

    Bhaskara P Achar
    22 views7 pages
    The document discusses crystalline structure in engineering materials. Crystalline solids have particles (atoms, molecules, ions) arranged in a definite repetitive geometric pattern with like neighbors. This periodic arrangement can be described by a lattice consisting of points in space. Any point in the 3D lattice is defined by a position vector based on integer multiples of three unit vectors a, b, c. Repeating this unit cell generates the crystal structure. There are 7 crystal systems based on the length and orientation of the unit vectors.

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    Crystal structure-Types

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    The document discusses crystalline structure in engineering materials. Crystalline solids have particles (atoms, molecules, ions) arranged in a definite repetitive geometric pattern with like neighbors. This periodic arrangement can be described by a lattice consisting of points in space. Any point in the 3D lattice is defined by a position vector based on integer multiples of three unit vectors a, b, c. Repeating this unit cell generates the crystal structure. There are 7 crystal systems based on the length and orientation of the unit vectors.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    22 views7 pages

    Crystal Structure-Types

    Uploaded by

    Bhaskara P Achar
    The document discusses crystalline structure in engineering materials. Crystalline solids have particles (atoms, molecules, ions) arranged in a definite repetitive geometric pattern with like neighbors. This periodic arrangement can be described by a lattice consisting of points in space. Any point in the 3D lattice is defined by a position vector based on integer multiples of three unit vectors a, b, c. Repeating this unit cell generates the crystal structure. There are 7 crystal systems based on the length and orientation of the unit vectors.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
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    of 7

    Engineering Materials

    MATERIAL

    SOLID LIQUID GAS PLASMA

    CRYSTALLINE
    Ionic and Metallic
    Bonds

    AMORPHOUS
    Covalent Bonds

    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 1


    Crystalline Structure

     In a crystalline solid, particles which may be (atoms, molecules or ions) are surrounded by
    like neighbors according to a definite geometrical repetitive pattern.
     When describing crystalline structures, atoms or ions are thought of as being solid spheres
    having well-defined diameters.

    How atoms
    are
    arranged ???

    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 2


    Crystalline Structure

     The periodicity of atoms in crystalline solids can be


    described by a network of points in space called lattice.
    A space lattice can be defined as a three dimensional
    array of points, each of which has identical surroundings.
    Position of any point along the line
    obtained by a simple translation
    a
    ru = ua
    ruv = ua+vb in a 2D plane,
    where u and v are integers.
    Crystalline Structure

    The position of any atom in the 3D lattice can be described by a vector


    ruvw= ua + vb + wc, where u, v and w are integers.

     Unit vectors, a, b, c can define a cell as


    shown by the shaded region in Fig.(a)
     This cell is known as unit cell (Fig. b)
     Unit cell when repeated in the three
    dimensions generates the crystal
    structure.

    Fig.(a)
    Fig.(b)
    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 4
    Crystalline Structure

    Bravais Lattice
     The unit vectors a, b and c are called lattice parameters.
     Based on their length equality or inequality and their orientation (the
    angles between them, α, β and γ) a total of 7 crystal systems can be
    defined.

    Cubic: a=b=c, α=β=γ=90°

    Body centered Face centered


    Simple
    Cubic (BCC) Cubic (FCC)
    Cubic

    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 5


    Crystalline Structure
    Orthorhombic: a≠b≠c, α=β=γ=90°

    Simple Body Body Base Face


    Simple
    tetragonal centered centered centered centered
    tetragonal

    Simple monoclinic Base centered


    monoclinic
    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 6
    Crystalline Structure

    Hexagonal closed
    Rhombohedral Hexagonal Triclinic
    packing
    a=b=c a=b≠c a≠b≠c
    α = β = γ ≠ 90° a=b≠c
    α = β = 90°, γ=120° α≠β≠γ≠90°
    α = β = 90°, γ=120°

    Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 7

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