Lattice dynamics and dielectric properties ofSiO2stishovite

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 ${\mathrm{SiO}}_2$ with sixfold coordinated silicon atoms. Comparsion 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.