A calculation of the phonon frequencies in sodium

Abstract

Abstract The phonon spectrum of sodium is calculated in the harmonic approximation. The effective interaction between the ions is separated into direct two-body forces between bare ions and effective attraction due to the presence of conduction electrons. Careful treatment of the two-phonon processes includes the calculation of the electron-phonon scattering based on the pseudo-potential method and the screening effects due to the interaction between electrons by the Hartree-Fock approximation with a screened exchange potential. Comparison of the results for sodium with neutron diffraction measurements and a previous calculation by Toya shows good agreement on the whole. It is hoped that this method may be applied to some other metals.