Phonon calculations for KCl ab initio

Abstract

A method is discussed whereby self-consistent calculations of quantities characteristics of specific optic phonons can be carried out ab initio. An application of the method is made to KCl which utilises the X alpha exchange scheme and the APW method. Results are presented for the first ever self-consistent charged density changes which accompany optic phonon excitation. These call into question methods for computing lattice vibration spectra which rely on assuming that only the outermost electron shells deform and move relative to the atomic nuclei during lattice vibrations.