Calculation of harmonic and cubic Einstein force constants in diamond-like crystals

Abstract

A theoretical discussion of isotropic and anisotropic single-particle potentials is presented. A model is developed for calculating the constants for diamond-structure carbon, silicon, germanium, and tin. Errors in the isotropic constants are +1%, -34%, -19%, and +35%. For the anisotropic constants errors are +7% and +22% for silicon and germanium. The temperature dependence of the potential constants is discussed through a charge-density theory for stretching force constants in molecules and solids.