3.4 x-ray diffraction

wavelength spacing is on the same order as ______

crystal spacings

constructive interferecne is

n*lambda

Destructive interference is where

½ * lambda

Diffraction angle is

2theta

X-rays that scatter off of deeper planes travel farther, resulting in

path length difference

general formula 1

2dsintheta = n lambda

changing the angle of incidence changes the ____ in path lengths

difference

only certain angles will result in

constructive intereference

to find interplanar spacing

d = nlambda/2sintheta

usually, first order diffraction implies

n = 1

the angle reported is actually

2 * angle

for a cubic system, the equation is

d = a / sqrt(h² + k² + l²)

what is ‘a’ in the interplanar spacing equation?

lattice parameter

to find lattice parameter, use

both equations

a higher symmetry crystal results in

fewer peaks

all planes in a family usually mean about

1 peak

more symmetric crystals have more planes belonging to a family, so

fewer peaks overall

Amorphous materials _______ distinct peaks in XRD

do not have

Every XRD pattern is

unique

the number of peaks is

based on symmetry and purity

the location of peaks is based on

interplanar spacing

how will the XRD pattern change if a crystal has impurities vs pure crystal

more impurities means more different spacings, thus more peaks

How will XRD pattern change if a crystal undergoes a structural phase transformation from a more symmetric phase to a less symmetric phase?

there will be more peaks due to more different families

how will XRD pattern change if the lattice parameter expands?

higher interplanar spacing (d), peaks will shift to smaller angle