PROPAGATING AND LOCALIZED VIBRATIONAL-MODES IN NI-ZR GLASSES

Numerical investigations of the vibrational eigenmodes of amorphous Ni xZr100-x alloys are presented. Structural models are prepared by molec ular dynamics simulations of the quenching processes, based on interat omic forces derived using a tight-binding-bond approach. The vibration al properties are investigated via a direct diagonalization of the dyn amical matrix for N = 729-atom models, and via recursion calculations of the vibrational spectral functions, partial and total dynamical str ucture factors and vibrational densities of states for large N = 2916- atom models. The static structure of the NixZr100-x glasses is charact erized by a pronounced chemical and topological short-range order (SRO ). We investigate in detail the manifestation of the SRO in the partia l dynamic spectral functions and structure factors S-IJ(k, omega). We discuss the possibility of measuring partial dynamic structure factors using inelastic neutron scattering and demonstrate that our results a re in good agreement with the existing experimental data on the total dynamical structure factors. We show that, although most eigenmodes ar e extended, localized modes can be found at the upper and lower edges of the frequency spectrum. Of particular interest is the prediction of low-energy localized modes, which have a profound influence on the lo w-temperature thermodynamic properties.