INTRINSIC LOCALIZED ANHARMONIC MODES AT CRYSTAL EDGES

Using a realistic lattice-dynamical model for a diatomic crystal, time-periodic anharmonic vibrations have been found with displacement pattern localized at an edge of the crystal. The localization is not only in the direction normal, but also in the directions parallel to the edge along which the lattice is periodic. These vibrational modes are three-dimensional analogs of the intrinsic localized modes studied earlier in linear chains or in higher-dimensional lattices with only a scalar degree of freedom per lattice site. The stability of these modes over times much longer than the vibrational period is tested and verified by molecular dynamics.