Calculation of reduced intensity functions for model amorphous structures, including coupling of thermal vibrations

摘要

Coupling of thermal vibrations was introduced into the calculation of the reduced intensity function for two model amorphous structures by using coupling coefficients which are a function of interatomic distance. A microcrystallite model of amorphous silicon and an ion cluster model of amorphous calcium phosphate were examined. Since coupling factors appropriate to these materials were not available, data from several different materials was used to estimate the importance of such coupling. Splitting of certain peaks in the diffraction pattern at high angles was found to be reduced, giving better agreement between calculated patterns and measurements on actual materials. These results suggest that coupled thermal vibrations and other random perturbations which affect large interatomic distances more than smaller ones may have a significant affect on the diffraction pattern.