### Acta Crystallographica Section A

# Foundations of Crystallography

### Volume 68, Part 1 (January 2012)

## research papers

*Acta Cryst.* (2012). A**68**, 68-76 [ doi:10.1107/S0108767311037779 ]

### Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors

**Abstract:** Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state *s* (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (*x* = 0, ..., 1 in 0.01 steps), where the lattice parameters for composition *x* in strain state *s* were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

**Keywords: scattering factors; static atomic displacements; modified atomic scattering amplitudes; correction factor.**

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