Volume heterogeneity in liquid Cu near the dynamical crossover temperature Ta

Abstract

We present the results of a molecular dynamics simulation in which we investigate whether a supercooled monometallic liquid exhibits structural heterogeneities. Using the voronoi construction, we calculate the atomic excess volume va and its distribution in liquid Cu in the 3D space. We find that va is not distributed homogeneously in the liquid, atoms with smaller va aggregate to form solid-like clusters which give rise to the dynamical heterogeneity. In the cooling process, these solid-like clusters increase rapidly from Ta showing the structural origin of dynamical crossover. we demonstrate that it is the excess volume of the cluster that governs the liquid dynamics below Ta. We also find that the atomistic motion is controlled by the excess volume of its neighbors demonstrating the enhancing collective motion feature below Ta.