Thermodynamic and Vapor-Liquid Equilibrium Properties of Deuterium from an Ab Initio-Based Intermolecular Potential
Ulrich K Deiters1, Richard J Sadus2
1Institute for Light and Matter, Faculty of Mathematics and Natural Sciences, University of Cologne, Greinstr 4-6, D-50939 Köln, Germany.
Abstract:
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 (D2). 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(H2) + 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.
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