Crystal lattice dynamics of various silicon-carbide polytypes

Abstract

A valence force field model with an added ionic interaction is applied to an explanation of phonon dispersion curves in 6H-SiC. The phonon dispersion curves in 3C-, 2H-, and 4H-SiC are calculated within the same model. Our results are compared with the published result of ab initio calculations. One can suppose that the present model may be applied for other polytypes of SiC. A phonon contribution to Helmholtz energy is determined for the simplest four polytypes. The results indicate a stability of hexagonal polytypes in relation to the cubic one at high temperatures.