Ab initio study of phonons in the rutile structure of SnO_2 under pressure

摘要

Using the local-density approximation, calculating the Hellmann-Feynman forces and applying the direct method, the phonon dispersion relations for the rutile-like structure of crystalline SnO_2 have been derived for the first time. The phonon frequencies at the Γ point agree very well with Raman and infrared data and other phenomenological model calculations. The LO/TO splitting is estimated by calculating phonons from an elongated supercell. The computations under pressure reveal a soft mode of B_(1g) symmetry which leads to a ferroelastic phase transition. The pressure-dependence of the lattice constants and the Gruneisen parameters of the modes are calculated.