Search for acoustic and optic vibrational modes in Zr-Be metallic glass

Dynamic structure factor of the Zr50Be50 metallic glass have been obtained by performing an inelastic scattering experiment on the BRISP spectrometer in the range of first pseudo-Brillouin-zone. We report the simultaneous observation of two density fluctuation modes in metallic glass with disparate mass components. Analysis of the dynamical parameters characterizing the two excitations reveals the acoustic nature of the low-energy mode and suggests an optic-like nature for the high energy mode.