High frequency acoustic modes in liquid gallium at the melting point

TL;DR

This study reveals that liquid gallium exhibits collective acoustic-like modes at high wave-vectors, supporting the idea of universal short-time dynamics in monatomic liquids despite its complex structure.

Contribution

It demonstrates the existence of high wave-vector acoustic modes in liquid gallium, contrasting previous neutron scattering results and suggesting universality in monatomic liquid dynamics.

Findings

Existence of collective acoustic modes above half the first maximum of the structure factor.

Liquid gallium's dynamics are similar to other simple liquids despite its complex structure.

Supports the universality of short-time dynamics in monatomic liquids.

Abstract

The microscopic dynamics in liquid gallium (l-Ga) at melting (T=315 K) has been studied by inelastic x-ray scattering. We demonstrate the existence of collective acoustic-like modes up to wave-vectors above one half of the first maximum of the static structure factor, at variance with earlier results from inelastic neutron scattering data [F.J. Bermejo et al. Phys. Rev. E 49, 3133 (1994)]. Despite the structural (an extremely rich polymorphism and rather complex phase diagram) and electronic (mixed valence) peculiarity of l-Ga, its collective dynamics is strikingly similar to the one of Van der Walls and alkali metals liquids. This result speaks in favor of the universality of the short time dynamics in monatomic liquids rather than of system-specific dynamics.