Computer simulation of liquid-vapor coexistence of confined quantum fluids

The liquid-vapor coexistence (LV) of bulk and confined quantum fluids has been studied by Monte Carlo computer simulation for particles interacting via a semiclassical effective pair potential V-eff (r) = V-LJ + V-Q, where V-LJ is the Lennard-Jones 12-6 potential (LJ) and V-Q is the first-order Wigner-Kirkwood (WK-1) quantum potential, that depends on beta = 1/kT and de Boer's quantumness parameter Lambda = h/sigma root m epsilon, where k and h are the Boltzmann's and Planck's constants, respectively, m is the particle's mass, T is the temperature of the system, and sigma and epsilon are the LJ potential parameters. The non-conformal properties of the system of particles interacting via the effective pair potential V-eff (r) are due to Lambda, since the LV phase diagram is modified by varying Lambda. We found that the WK-1 system gives an accurate description of the LV coexistence for bulk phases of several quantum fluids, obtained by the Gibbs Ensemble Monte Carlo method (GEMC). Confinement effects were introduced using the Canonical Ensemble (NVT) to simulate quantum fluids contained within parallel hard walls separated by a distance L-p, within the range 2 sigma <= L-p <= 6 sigma. The critical temperature of the system is reduced by decreasing L-p and increasing Lambda, and the liquid-vapor transition is not longer observed for L-p/sigma < 2, in contrast to what has been observed for the classical system. (C) 2013 AIP Publishing LLC.