Lattice dynamics of the high-T/sub c/ superconductor YBa2Cu3O/sub 7-//sub x/

We present a lattice dynamical calculation of the phonon dispersion curves and the one-phonon density of states of the high-T/sub c/ superconductor YBa2Cu3O/sub 7-//sub x/ in the framework of a shell model, which is based on short-range overlap and long-range Coulomb potentials. The parameters of these potentials are obtained from best fits to the measured phonon dispersion curves of BaTiO3 and appropriate metal oxides. The model for YBa2Cu3O/sub 7-//sub x/ so obtained leads to rather satisfactory agreement with the available ir and Raman data without any major adjustments of the potential parameters. These results thus provide a solid basis for the discussion of the role of phonons for the high transition temperature and a guide for further experimental studies of the vibrational properties of this and related compounds