A quantum Monte Carlo study of liquid Lennard-Jones methane, path-integral and effective potentials

Abstract

An intercomparative quantum study of liquid methane over a range of temperatures at zero experimental vapour pressure is presented. Interest is focused on the translational features. Classical, semi-classical (Wigner-Kirkwood (ħ²), Feynman-Hibbs) and path-integral Monte Carlo simulations have been performed. A basic one-centre Lennard-Jones potential has been used as the basic model to carry out computations. Energies, pressures and pair radial distribution functions are reported, and the reliability of the effective potentials is discussed. The results indicate, first, important quantum effects on the structure of this liquid and, second, that the Wigner-Kirkwood potential is a better semi-classical choice.