ABSTRACT
Static atomic displacements (SDs) from the average crystal sites exist in all III-V alloys where atoms having different covalent radii share a common sublattice. This chapter shows that the SDs may have a large effect for reflections with low structure fuctors. It also shows that the SDs must be taken into account, in particular when such 'quasi-forbidden' reflections are used to measure the local alloy composition. The chapter investigates another possible cause of deviation between the SF and Fhkl. It demonstrates that SDs have a significant effect on the SFs of low intensity reflections and that they should be taken into account in accurate image calculations. The SDs depend not only on the atomic configurations but also on the strain state of the crystal.
