Calculation of thermodynamic properties of neon with ab initio potentials using path integral and semiclassical Monte Carlo simulations

Path integral Monte Carlo and semiclassical Monte Carlo simulations using the Feynman-Hibbs corrections to account for nuclear quantum effects were employed to calculate ten different thermodynamic properties of the noble gas neon in the isobaric-isothermal ensemble. As path integral simulations could only be carried out for small systems due to the large required computational resources, while semiclassical simulations can be performed for much larger systems, an extrapolation scheme was developed to obtain results in the quantum-mechanical and thermodynamic limits, which utilizes the similar dependence of results for thermodynamic properties on the system size in both simulation techniques. This approach yields accurate results for macroscopic thermodynamic properties and additionally allows the assessment of the validity of the Feynman-Hibbs corrections in the studied region of the phase diagram. A total of 38 state points were simulated at eight isotherms between 27.5 and 100 K, covering the liquid and supercritical regions of the phase diagram at pressures up to 90 MPa. The interactions between the neon atoms were described by highly accurate state-of-the-art ab initio potentials for both pairwise and nonadditive three-body contributions. The predicted densities and speeds of sound at the isotherms 80 and 100 K agree with the most accurate experimental data from the literature within the mutual uncertainties. At lower temperatures, our results are likely more accurate than the available experimental data for the density and speed of sound.