Anomalies in the Surface-Phonon Dispersion of TiN(001)

The TiN(001) surface phonons are studied by the Green's-function method. The electron-phonon interaction is described by the coupling of the electronic charge-density deformations to the nuclear displacements. Anomalies in the surface dispersion curves are found at half the distance to the boundary of the Brillouin zone in the [100] direction. The calculated surface density of states is in good agreement with that measured by Rieder and Drexel. It is suggested that the investigation of surface-phonon anomalies permits us to check the validity of bulk dynamical models.