SiC up to 35 GPa: Eos, phonon dispersion curves and sum rule. polytypes 6H and 15R

Abstract
Lattice parameters for SiC-15R and phonon frequencies for SiC-15R and SiC-6H were investigated as function of pressure by X-ray single crystal analysis and first-order Raman scattering. Linear and bulk moduli and phonon Gruneisen parameters were obtained. Phonon dispersion curves plotted in the standard large zone reveal certain softening of the TA-branch at the zone boundary. The nature of the covalent systems stability is discussed in the light of the sum rule.