Molar excess volumes of liquid hydrogen and neon mixtures from path integral simulation

Volumetric properties of liquid mixtures of neon and hydrogen have been cal culated using path integral hybrid Monte Carlo simulations. Realistic poten tials have been used for the three interactions involved. Molar volumes and excess volumes of these mixtures have been evaluated for various compositi ons at 29 and 31.14 K, and 30 atm. Significant quantum effects are observed in molar volumes. Quantum simulations agree well with experimental molar v olumes. Calculated excess volumes agree qualitatively with experimental val ues. However, contrary to the existing understanding that large positive de viations from ideal mixtures are caused due to quantum effects in Ne-H-2 mi xtures, both classical as well as quantum simulations predict the large pos itive deviations from ideal mixtures. Further investigations using two othe r Ne-H-2 potentials of Lennard-Jones (LJ) type show that excess volumes are very sensitive to the cross-interaction potential. We conclude that the cr oss-interaction potential employed in our simulations is accurate for volum etric properties. This potential is more repulsive compared to the two LJ p otentials tested, which have been obtained by two different combining rules . This repulsion and a comparatively lower potential well depth can explain the positive deviations from ideal mixing. (C) 1999 American Institute of Physics. [S0021-9606(99)50926-4].