Electronic polarizability effects on the anharmonic phonon shift and damping in ionic crystals

A. GRECO; S. KOVAL; R. MIGONI

Pichidangui

Simposio; XII Simposio Latinoamericano de Física del Estado Sólido, SLAFES; 1992

Abstract:The authors apply a previously developed perturbative formalism for anharmonic shell models to the calculation of phonon shifts and widths in a one-dimensional model of a solid with polarizable ions. They analyse these properties for different k-points in the Brillouin zone and also as a function of temperature for fixed k. They compare the results for several values of the core-shell coupling constant g with those obtained by using a rigid-ion model (g to infinity ). They show that the electronic polarizability of ions leads to significant modifications of the k-dependences as well as of the ratio between the damping and shift. They give an interpretaton of existing discrepancies between theory and experiment for anharmonic phonons in silicon. Finally, they mention some further applications.