Monte Carlo Study of Short-Range Order and Displacement Effects in Disordered CuAu

TL;DR

This study uses Monte Carlo simulations to explore how local atomic environments influence displacements in disordered CuAu alloys, revealing environment-dependent distances and effects of short-range order on atomic spacing.

Contribution

It demonstrates the effectiveness of Monte Carlo simulations based on effective medium theory in accurately modeling local chemical and displacement correlations in disordered CuAu alloys.

Findings

Chemically-specific pair distances depend on local environment.

Short-range order decreases Cu-Au distances below Cu-Cu distances.

Trends explained by differences in atomic radii and compressibilities.

Abstract

The correlation between local chemical environment and atomic displacements in disordered CuAu alloy has been studied using Monte Carlo simulations based on the effective medium theory (EMT) of metallic cohesion. These simulations correctly reproduce the chemically-specific nearest-neighbor distances in the random alloy across the entire Cu\$_x\$Au\$_{1-x}\$ concentration range. In the random equiatomic CuAu alloy, the chemically specific pair distances depend strongly on the local atomic environment (i.e. fraction of like/unlike nearest neighbors). In CuAu alloy with short-range order, the relationship between local environment and displacements remains qualitatively similar. However the increase in short-range order causes the average Cu-Au distance to decrease below the average Cu-Cu distance, as it does in the ordered CuAuI phase. Many of these trends can be understood qualitatively from the different neutral sphere radii and compressibilities of the Cu and Au atoms.