Anharmonic self-energies of phonons in silicon

Abstract

We have carried out a realistic ab initio calculation of the contribution of cubic anharmonicity to the inverse lifetime Γ and the frequency shift Δ of phonons in silicon. The cubic coupling constants for phonons throughout the Brillouin zone are obtained from an anharmonic Keating-type lattice-dynamical model, which has been fit to a database of results from local-density-approximation frozen-phonon and elastic-modulus calculations. Γ and Δ have been calculated as a function of temperature T and wave vector. Our results agree reasonably well with experiment, but indicate the need for retention for quartic and higher-order terms, especially at high T.