# Atomic Form Factor

1. Oct 21, 2014

### Lemenks

1. The problem statement, all variables and given/known data

I am trying to calculate the atomic form factor for various crystals (NaCl, LiF, GaP, Si) in an x-ray diffraction experiment.

There seems to be very little information on this topic anywhere.

2. Relevant equations

I understand how to derive the geometric form factor Sk = sum of exp[i.pi.K.r]

And the atomic form factor is Sk = ∑exp[i.pi.K.r].fj

Where fj(K) = -1/e ∫dr exp[i.K.r].pj(r)

3. The attempt at a solution

For a BCC lattice Sk = 1+(-1)^n1+n2+n3 -monatomic
My guess is that I sub in Sk = f1(1) + f2(-1)^n1+n2+n3

I am not sure if this is correct and how I can generalize it, any help would be appreciated. Thanks.

2. Oct 22, 2014

### nasu

The atomic form factor does not depend on the type of crystal. Is a characteristic of the atom. You can find it in literature or databases, for each atom, as a function of angle and wavelength.

It looks like you are trying to calculate the structure factor of various lattices and not the atomic form factor. Isn't that so?

3. Oct 22, 2014

### Lemenks

Ohh, I actually made a mistake,

fj(K) is the actual atomic form factor, I solved the geometric form factor for a BCC lattice but I am struggling to add in the atomic form factor. ~ I guessed that I simply multiply each geometric form factor answer for a BCC lattice by each atomic form factor but honestly I don't really know and I can't find any texts on it.

4. Oct 22, 2014