Our paper entitled Equation of state and force fields for Feynman–Hibbs-corrected Mie fluids. II. Application to mixtures of helium, neon, hydrogen, and deuterium becomes Editors pick in J. Chem. Phys.
In the paper, we extend the statistical associating fluid theory of quantum corrected Mie potentials (SAFT-VRQ Mie), previously developed for pure fluids, to fluid mixtures. In this model, particles interact via Mie potentials with Feynman–Hibbs quantum corrections of first order (Mie-FH1) or second order (Mie-FH2). This is done using a third-order Barker–Henderson expansion of the Helmholtz energy from a non-additive hard-sphere reference system. We survey existing experimental measurements and ab initio calculations of thermodynamic properties of mixtures of neon, helium, deuterium, and hydrogen and use them to optimize the Mie-FH1 and Mie-FH2 force fields for binary interactions. Simulations employing the optimized force fields are shown to follow the experimental results closely over the entire phase envelopes. SAFT-VRQ Mie reproduces results from simulations employing these force fields, with the exception of near-critical states for mixtures containing helium. This breakdown is explained in terms of the extremely low dispersive energy of helium and the challenges inherent in current implementations of the Barker–Henderson expansion for mixtures. The interaction parameters of two cubic equations of state (Soave–Redlich–Kwong and Peng–Robinson) are also fitted to experiments and used as performance benchmarks. There are large gaps in the ranges and properties that have been experimentally measured for these systems, making the force fields presented especially useful.
The paper is one of the last papers in the PhD thesis of Ailo Aasen , but several people have made significant contributions to the work, such as Morten Hammer at SINTEF Energy Research and Erich A. Müller from Imperial College in London. The figure below shows a comparison to experimental results for the Helium-Neon mixture (crosses) and the first accurate theoretical description of this mixture (bullet points). The perturbation theory for mixtures (solid lines) still needs some more development before it can cope with the challenging aspects of quantum fluid mixtures.