The Geometry of Slow Structural Fluctuations in a Supercooled Binary Alloy

TL;DR

This study uses molecular dynamics simulations to explore the structure and fluctuations of supercooled binary alloys, revealing that cluster fluctuations are linked to thermodynamic and dynamic slowdowns during cooling.

Contribution

It introduces a combined analysis method revealing the role of Frank-Kasper clusters in the slow dynamics of supercooled alloys.

Findings

Clusters have the same short-range order as the crystal.

Fluctuations in clusters correlate with inherent structure energy.

Heat capacity increase is linked to cluster fluctuation growth.

Abstract

The liquid structure of a glass-forming binary alloy is studied using molecular dynamics simulations. The analysis combines common neighbour analysis with the geometrical approach of Frank and Kasper to establish that the supercooled liquid contains extended clusters characterised by the same short range order as the crystal. Fluctuations in these clusters exhibit strong correlations with fluctuations in the inherent structure energy. The steep increase in the heat capacity on cooling is, thus, directly coupled to the growing fluctuations of the Frank-Kasper clusters. The relaxation of particles in the clusters dominates the slow tail of the self-intermediate scattering function.