LATTICE-DYNAMICS AND DIELECTRIC-PROPERTIES OF SIO2 STISHOVITE

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