Atomistic Simulation of the Coexistence of Liquid–Vapor Phase States for Gold and Determination of Critical Parameters

摘要

Abstract The work is devoted to the study (on the example of gold) of the properties of metals near the critical point. Long-term studies testify to the complexity of the problem and its importance both for constructing theoretical ideas about the behavior of metastable states of a highly superheated liquid phase of metals and for developing a number of technological applications in the field of materials science, the impact of concentrated energy flows on a substance, etc. Metastable states of a superheated liquid and a saturated vapor in the vicinity of the critical point have not been sufficiently studied. When approaching the critical point, the properties of matter change dramatically due to strong stochastic fluctuations of parameters (primarily density). Molecular dynamics (MD) methods are a relevant tool for determining critical parameters. For gold, they were used to obtain a liquid–vapor coexistence curve, from which the critical parameters were then determined: temperature, density, and pressure. In the calculations, the potential of the family of “embedded atom method” (EAM) was used as the interaction potential of particles. The value of the critical temperature Tcr was determined from the results of MD simulation using the method of the maximum size of the averaged cluster on the temperature curve passing through the critical region. The value of the critical pressure Pcr was obtained from the results of MD simulation from the temperature dependence of the saturated vapor pressure Psat(T). The value of the critical density ρcr was obtained from the results of MD simulation of the liquid–vapor coexistence curve using the empirical rule of the rectilinear diameter. The simulation results of this work are compared with the results of estimation of the critical parameters of gold by other authors using different approaches.