Nonequilibrium, highly inhomogeneous melting in the microcanonical ensemble

Homogeneous melting of a crystal is mediated by forming a metastable solid phase, in which vacancy–interstitial pairs and other more complex defects are created, as shown by microcanonical computer simulation during the last two decades. Additionally, highly inhomogeneous melting has gained the most interest because of its presence in experiments, such as laser impact. Understanding the fundamentals of this highly inhomogeneous melting will allow us to project these phenomena both to theory and applied cases. In this work, we present evidence via molecular dynamics simulations of a metastable solid phase in BCC tungsten produced from a highly inhomogeneous, nonequilibrium initial condition where a single atom contributes kinetic energy of approximately 0.74 keV. Despite the striking difference between this highly inhomogeneous energy injection and homogeneous melting (as is implemented, for instance, in the Z-method), the obtained critical superheated solid-state has a lifetime reaching up to 200 ps and can be described by a waiting time distribution, in qualitative agreement with previous studies on superheating.