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

Abstract

In this work, we investigate the melting behavior of equiatomic Ag–Zr using molecular dynamics simulations, combining analyses of thermodynamic response, local structure, chemical short-range order, and atomic dynamics. A characteristic melting temperature near 1400 K is determined from the heat-capacity maximum within a broader melting range of ∼1350–1500 K, supported by the consistent evolution of energy, heat capacity, and atomic-scale descriptors. The melting transition is accompanied by the destabilization of first-neighbor coordination, manifested by a decrease in coordination number, a significant loss of chemical short-range order, and enhanced heteroatomic mixing. This local instability also leads to the attenuation of medium-range correlations, a decline in crystalline environments identified by CNA, and reduced 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. These results demonstrate that melting in Ag–Zr is governed by a cooperative structural–chemical–dynamical instability rather than a single thermodynamic or displacement-based criterion.