Ab initio and phenomenological simulation of the phonon spectra BeMN2 (M = C, Si, Ge, Sn) crystals

Abstract

Phonon spectra of hypothetic BeMN₂ (M = C, Si, Ge, Sn) crystals with a chalcopyrite lattice are calculated by the ab initio density functonal method in the center of the Brillouin zone and interpolated over the whole Brillouin zone using the phenomenological Keating model. Interaction parameters are found by comparing IR and Raman active frequencies obtained in the phenomenological model with calculations performed by the ab initio method. Numerical values of short-range constants and charges are in accordance with the ab initio calculated characteristics of the chemical bond. These parameters have the obvious physical meaning and the chemical nature and can be further used for both qualitative estimates of any physical and physicochemical values and quantitative calculations of the phonon spectra of isostructural compounds.