Interchain Forces in the Lattice Dynamics of Trigonal Se and Te

Abstract

Valence force field calculations of the lattice dynamics of trigonal Se and Te have not been able to provide a good description of the elastic constants and long wavelength optic modes. We have developed a more complete description of the inter-chain forces that is based on the directional character of these bonds and that considers a competition between the primary intra-chain bonds and the secondary inter-chain bonds. This approaches provides a good description of the phonon dispersion, and accounts for other properties as well, e.g., the pressure dependence of the Raman modes.