Structural effect on phonon attenuation in metallic liquids and glasses

TL;DR

This study investigates how structural coherence influences phonon attenuation in metallic liquids and glasses, revealing a correlation between wavevector crossover and density correlations, and proposing a scattering mechanism involving low-energy structural activations.

Contribution

It demonstrates the link between structural coherence length and phonon attenuation crossover in metallic systems using molecular dynamics simulations.

Findings

Crossover wavevector correlates with structural coherence length.

Linear attenuation arises from scattering by low-energy structural activations.

The behavior varies between metallic liquids and glasses.

Abstract

The attenuation rate of vibrational excitations in various metallic liquids and glasses has been reported to change from the quadratic dependence on wavevector at low wavevectors to the linear dependence at high wavevectors. However, the origin of this behavior is not clear. Here, the analysis of this phenomenon through molecular dynamics is presented for prototypical metallic liquids, Cu56Zr44 and Fe. It is shown that the crossover wavevector is strongly correlated with the structural coherence length characterizing coarse-grained density correlations. We suggest that the linear dependence is caused by scattering of vibrational excitations by structural activation processes with low activation energies which are distinctively observed in metallic systems.