A direct approach to calculate the phonon dispersion using an ab initio force constant method is introduced. The phonon dispersion and structural instability of cubic ZrO2 are found using a supercell method in the local-density approximation. The force constants are determined from the Hellmann-Feynman forces induced by the displacement of an atom in the 2×2×2 fcc supercell. This size of the supercell gives “exact” phonon frequencies at γ, X, L, W Brillouin zone points. The phonon dispersion curves show a pronounced soft mode at the X point, in agreement with the experimentally observed cubic to tetragonal phase transition.
ASJC Scopus subject areas
- Physics and Astronomy(all)