Path-integral Monte Carlo simulations of a supercritical fluid

Path-integral Monte Carlo simulations are carried out for a fluid over a wide temperature range and at a pressure above the critical pressure. The simulations are applied to a system consisting of 500 atoms that interact through a truncated Lennard-Jones potential, and which have the atomic masses and interaction parameters of xenon, argon, or neon. The thermal-expansion coefficient and the constant-pressure heat capacity are determined as a function of temperature. The simulations show that the effective glass transition evident in classical simulations, which is discerned from a sharp change in the thermal-expansion coefficient and heat capacity, is obscured by quantum-mechanical effects in these systems. It is also shown that the thermal-expansion coefficient in the fluid phase converges to the classical result at a low temperature, in comparison to the heat capacity in the fluid phase and the thermal-expansion coefficient in the crystal phase.