Thermodynamic and Vapor–Liquid Equilibrium Properties of Deuterium from an <i>Ab Initio</i> -Based Intermolecular Potential

Molecular simulation with an ab initio -based intermolecular potential is used to investigate the atomic-level interactions responsible for the thermodynamic properties and vapor–liquid-equilibria (VLE) of deuterium (D 2 ). Results are reported for pressures up to 100 MPa at both low (cryogenic) and ambient temperatures. The combination of a simplified ab initio atomic potential (SAAP) with Feynman–Hibbs first order (FH1) interactions closely reproduces the VLE phase envelope over a wide range of densities, resulting in good estimates of the critical properties. It also accurately reproduces the behavior of the second virial coefficient and pressure–temperature–volume properties. The analysis indicates that deuterium and hydrogen share the same intermolecular potential, i.e., SAAP(H 2 ) + FH1. Additional quantum corrections to the kinetic energy (QCKE) are used to determine the enthalpy, heat capacities, isochoric pressure coefficient, isobaric thermal expansion coefficient, Joule–Thomson coefficient and the speed of sound. At cryogenic conditions, using QCKE yields close agreement with reference values for these properties.