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Thermophysics and Aeromechanics

2013 year, number 1

Melting line, spinodal and the endpoint of the melting line in the system with a modified LennardJones potential

S.P. Protsenko, V.G. Baidakov, and A.O. Tipeev
Institute of Thermophysics UrB RAS, Yekaterinburg, Russia
baidakov@itp.uran.ru
Keywords: molecular dynamics, LennardJones fluid, melting line, spinodal, metastable state
Pages: 95-106

Abstract

A molecular dynamics method was used to calculate the pressure p* and the internal energy e* of a liquid and a crystal in stable and metastable states in a system of 2048 particles, which interaction is described by a modified Lennard—Jones potential. For the liquid phase, calculations were performed along 13 isotherms from the range of reduced temperature T*=0.35-3.0, and for the crystal phase, along 16 isotherms from the range T*=0.1-3.0. The thermal p*=p*(ρ*, T*) and caloric e*=e*(ρ*, T*) equations of state for liquids and crystals have been constructed. The parameters of crystal–liquid phase equilibrium have been determined from the conditions of phases coexistence at positive pressures and in the region of negative pressures, where the coexistent phases are metastable. The spinodal of a stretched liquid has been approximated. It has been found that with a temperature decrease the metastable extension of the melting line meets the spinodal of the liquid phase. The point of their meeting, the endpoint of the melting curve, is the point of termination of crystalliquid phase equilibrium without the onset of identity of the phases.