Connection between vibrational dynamics and topological order in simple glasses

We compare vibrational dynamics in two structurally distinct, simple monatomic model glasses simulated by molecular dynamics: the Lennard-Jones glass with an fcc-related structure and a glass with predominantly icosahedral short-range order. The former, characterised by a single local quasi-periodicity, supports only modes with acoustic behaviour. In the latter, the presence of optic modes and two incommensurate length scales is observed. This pattern of vibrational dynamics is shown to be closely related to that of a Frank-Kasper crystal having the same local topological order.