Mean-square amplitudes of vibration for ionic crystals

Abstract

Detailed calculations are presented of the mean-square amplitudes of vibration of atoms in 20 alkali halides and four alkaline-earth oxides. The results are presented from 10\ifmmode^\circ\else\textdegree\fi{}K to the melting temperatures. The computation has been carried out by setting up the dynamical matrix for a shell model and calculating the eigenvalues and eigenvectors at a number of points in the reciprocal space. Shell-model parameters fitted to neutron data available for NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, LiF, CsF, CsCl, CsBr, CsI, MgO, and CaO have been used in the computation. For five crystals, LiCl, LiBr, LiI, SrO, and BaO, the shell-model parameters have been computed using experimental data on elastic constants, ir optical and dielectric parameters. The theoretical results have been compared with the x-ray scattering and M\ossbauer data.