Simulation of thermal diffuse scattering including a detailed phonon dispersion curve

Thermal vibration of the atoms in a crystal give rise to a diffuse backgrou nd in the diffraction pattern (in between the normal allowed Bragg reflecti ons), The Einstein model for phonon vibrations in a crystal leads to Gaussi an statistics for the phonons, However, the Einstein model ignores the poss ibility of correlation between the atoms. An accurate model of the phonon d ispersion curves for silicon is used to generate a set of more accurate ran dom atomic displacements. These displacements are used in a multislice-styl e simulation to gauge the validity of the Einstein approximation. The phono n dispersion curve yields a small additional oscillatory structure in the t hermal diffuse scattering (TDS) pattern. This does not produce significant changes in the annular dark field scanning transmission electron microscope (ADF-STEM) image signal, but could have a large impact on convergent beam measurements of bond charges, (C) 2001 Published by Elsevier Science B.V.