Communication: Ab initio Joule–Thomson inversion data for argon

Abstract

The Joule–Thomson coefficient μH(P, T) is computed from the virial equation of state up to seventh-order for argon obtained from accurate ab initio data. Higher-order corrections become increasingly more important to fit the low-temperature and low-pressure regime and to avoid the early onset of divergence in the Joule–Thomson inversion curve. Good agreement with experiment is obtained for temperatures T > 250 K. The results also illustrate the limitations of the virial equation in regions close to the critical temperature.

Eighth-Order Virial Equation of State for Methane from Accurate Two-Body and Nonadditive Three-Body Intermolecular Potentials

“…The inversion temperature difference is largest at the upper ends of the two curves, which, as discussed above, are at 952.9 K for the VEOS and at 980.3 K for the SWEOS. Considering that the SWEOS is only valid up to 625 K, we believe that the inversion curve predicted by VEOS8 is much more accurate than that of the SWEOS above 625 K. We note that the curves shown in Figure for VEOS3 to VEOS7 are remarkably similar in shape to those computed by Wiebke et al . for argon using the VEOS of Jäger et al …”

“…remarkably similar in shape to those computed by Wiebke et al45 for argon using the VEOS of Jager et al13 …”

Three-Body Nonadditive Potential for Argon with Estimated Uncertainties and Third Virial Coefficient

“…The aim of the present work was to develop a state-of-the-art three-body argon potential, including uncertainty estimates at each calculated point, and to calculate the third virial coefficients at the full quantum level. Equations of state based on the virial series can be applied to calculate many thermodynamic properties for gaseous argon, ,− and the third virial coefficients computed by us can be used in future studies of this type.…”

Can an Ab Initio Three-Body Virial Equation Describe the Mercury Gas Phase?

“…24,25 However, for prototypical systems such as Ar, this regime is sufficiently large for a seventh-order ab initio virial EOS of Ar to reproduce a range of bulk properties to remarkable accuracy. 19,26,27 Our motivation for the work reported here is at least twofold. First, a number of simple parametrizations of the low-density vapor EOS have been reported as (formally) second-order virial EOSs, 28−30 usually collecting non-ideality corrections in a term k B TB ̃2ρ 2 with B ̃2 ∝ 1/T 2 .…”

“…Therefore, although eq implies the limit N → ∞, B n is a functional of the terms in eq up to and including order n only. Recent reformulations , of Mayer et al’s (and later Ree’s and Hoover’s) diagrammatic schemes significantly reduce the number of diagrams required to evaluate the B n coefficients numerically and have been coupled to sophisticated Monte Carlo integrators. ,, Consequently, for systems with many-body expansions of the interaction energy E converging reasonably fast, virial coefficients and EOSs have been reported to rather high orders, ,− most notably up to order 5 for H 2 O, up to 7 for Ar from ab initio two- and three-body potentials, up to 8 for a Lennard-Jones system, , and up to order 10 and 12 for a soft-core and hard-core model, respectively. ,, We note in passing that the regime of applicability of eq is suggested to be more strongly restricted than by the (generally unknown) radius of convergence of the density expansion alone. , However, for prototypical systems such as Ar, this regime is sufficiently large for a seventh-order ab initio virial EOS of Ar to reproduce a range of bulk properties to remarkable accuracy. ,, …”