8 XRD
8 XRD
8 XRD
GE+EH = nλ
θ’
≠ nλ
GE + EH is the path difference, waves add if equal to nλ
X-ray Crystallography Methods:
Single-Crystal: Precession
Powder
Easiest
Infinite orientations at once, so only need to vary q ,
the angle of the incident beam of x-ray light.
Powder Diffraction Method
Requires random
orientation of very fine
crystals
Incident beam of a certain
X-ray wavelength will
diffract from atomic
planes oriented at the
appropriate θ angles for
the characteristic d
spacing
Random orientation of
crystals will produce more
intense diffraction peaks
for particular angles that
correspond to
characteristic atomic
planes
Powder Diffraction Plots
θ = arcsin (nλ / 2d)
λ(Cu) = 1.54Å
d - Qtz [101] = 3.342
θ = 13.32° ; 2θ = 26.64°
Quartz
Interpreting X-ray data
We will use the data obtained to
identify the mineral
determine the dimensions of the unit
cell.