# Determine the intensities of GaAs crystal planes

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1. Mar 3, 2015

### ralden

GaAs crystal structures have basis atoms:

Ga: (0 0 0), (0.5 0.5 0),(0.5 0 0.5),(0 0.5 0.5)
As: (0.25 0.25 0.25),(0.75 0.75 0.25),(0.75 0.25 0.75),(0.25 0.75 0.75)

i'm trying to find intensities at all of its plane, using this equation:

I = (F^2)*m*Lf (m= multiplicity, Lf=lorentz factor)

where F = f*cos(2*pi*(hx +ky +zl)), (f =atomic scattering factor)

or you could used:the simplest form:
F^2 = 16(fGa^2 + fAs^2 + 2f*Ga*fAs*(cos(90*(h+ k +)l)) )

but using this equation you would have peaks at 001 plane and other planes that base on literature would generate a zero Intensity,

so my problem was, are my equations or the F^2 simplest form are correct?

2. Mar 5, 2015

### M Quack

GaAs is FCC, so (100) peaks are forbidden.

With such structure factor formulae, it is always assumed that the peak exists to begin with. Otherwise you could calculate a non-zero structure factor even for non-integer values of hkl - which clearly do not give a Bragg peak.