LATTICE-DYNAMICS AND DIELECTRIC-PROPERTIES OF SIO2 STISHOVITE

Using the variational density-functional perturbation theory, we compute the phonon band structure, the interatomic force constants, the dielectric tensor, and the Born effective charge tensors of stishovite, a crystalline form of SiO2 with sixfold coordinated silicon atoms. Comparison with available experimental data shows agreement at the level of a few percent. Access to the real-space interatomic force constants allows us to analyze the interplay between long-range ionic interaction and short-range covalent bonding, as well as criticize available two-body interatomic potentials.