Crystal Indexing
1. The angle measured in the lab is between k and k’, thus it correspond to 2θ, where θ
is the angle in the Bragg law
2. Using the Bragg’s law and the wave length of the incoming radiaion, calculate dhkl for
all available peaks
3. Pick one as a reference d(h1k1l1) and take the ratio of d2(h1k1l1)/ d2(h2k2l2)
(recognizing that this ratio should correspond to h22+k22+l22/h12+k12+l12 by the
relation: d2=a2/(h2+k2+l2)
4. Multiply this ratio by an integer of increasing magnitude until all are whole numbers.
Or if the crystal structure is known, multiply until all planes are consistent with that
structure. This is equivalent to applying extinction rules for the crystal structure type
5. Using d and a single set of {hkl} planes, calculate a=d x sqrt(h2+k2+l2) (notice that
the same value of a should be obtained regardless which set of {hkl} are used
Extinction Rules
The following are the relationship that the vi must meet for a particular peak to show up
sc: all peak will show up
bcc: h+k+l=even
fcc: h, k, and l ALL odd or ALL even
diamond:( h, k, and l ALL even AND h+k+l =4n with n an integer) or (h, k, and l ALL
odd)
Problem
Solution