Monte Carlo study of short-range order and displacement effects in disordered CuAu

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 of metallic cohesion. These simulations correctly reproduce the chemically specific nearest-neighbour distances in the random alloy across the entire CU_xAU_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 neighbours). 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.