Surface Lattice Dynamics of Ionic Crystals by the Green Function Method

It is shown that the surface lattice vibrations of semiinfinite ionic crystals can be easily studied and calculated by an approximate Green's function method based on a suitably defined effective short‐range perturbation. Breathing shell model calculations for the (001) surface of NaCl are presented and compared with the direct lattice‐dynamical calculation carried out by Chen et al. for a 15‐layer slab. The reliability and the computational advantages of the Green's function technique with respect to the slab method are discussed in connection with the calculation of the surface phonon response functions.