Atomic displacement effects in near-edge resonant ¿forbidden¿ reflections

A survey of atomic displacement effects in the resonant scattering of synchrotron radiation is presented. It is shown that the dynamical displacements, associated with thermal vibrations, provide the thermal-motion-induced (TMI) “forbidden” reflections, while static displacements (e.g. induced by impurities) provide the point-defect-induced (PDI) “forbidden” reflections. Both kinds of reflections occur owing to perturbation of valent electrons wave functions by atomic displacements. The results of numerical calculations of TMI forbidden reflections in Ge and ZnO are compared with experimental data.