Coupled structural, chemical, and dynamical destabilization during melting of equiatomic Ag-Zr: a molecular dynamics study

Abstract

In this work, the melting behavior of equiatomic Ag-Zr is investigated by molecular dynamics simulations through a combined analysis of thermodynamic response, local structure, chemical short-range order, and atomic dynamics. A characteristic thermodynamic melting temperature near 1400 K is identified from the heat-capacity maximum within a broader melting interval of ~1350-1500 K, as supported by the consistent evolution of energy, heat capacity, and atomicscale descriptors. The transition is initiated by the destabilization of the first-neighbor coordination structure, manifested by a reduction in coordination number, collapse of chemical short-range order, and increased heteroatomic mixing. This local instability is accompanied by the attenuation of medium-range correlations, the depletion of CNA-identified crystalline environments, and a reduction in bond-orientational order. These structural and chemical changes occur within the same melting range of ~1350-1500 K and are accompanied by a pronounced dynamical crossover, characterized by a rapid decrease in structural relaxation time and the onset of fast configurational decorrelation. The results demonstrate that melting in Ag-Zr is governed by a cooperative structural-chemical-dynamical instability rather than by a single thermodynamic or displacement-based criterion.