A1 g phonons in YBa2Cu3O7 by first-principles atomic-force calculations

We report on ab-initio frozen-phonon calculations for the five A_1g Raman-active-modes of YBa₂Cu₃O₇ atq=0. The determination of the equilibrium positions of the atoms Ba, Cu(2), O(2), O(3), O(4) as well as of phonon frequencies and respective eigenvectors is based on the calculation of atomic forces within the LAPW-method. The general agreement between our results and experimental structural data and phonon frequencies is good. Deviations are discussed in connection with the local-density approximation.