The last article from Vilde Bråten, Daniel Tianhou Zhang, Morten Hammer, Ailo Aasen, Sondre Schnell and Øivind Wilhelmsen, all members at PoreLab, on “Equation of state for confined fluids” has been chosen as Featured Article by the Journal of Chemical Physics. The journal wrote the following: “Editors felt that your article was one of the journal’s best, and have chosen to promote it as a Featured Article. Once published, your paper will be displayed prominently on the journal’s homepage and will be identified with an icon next to the article title“.
In addition the topic was selected as a Scilight. Scilights showcase the most interesting research across the physical sciences published in AIP Publishing Journals.
Congratulations to the team!
Fluids confined in small volumes behave differently than fluids in bulk systems. For bulk systems, a compact summary of the system’s thermodynamic properties is provided by equations of state. For confined fluids, however, there is currently a lack of successful methods to predict thermodynamic properties by use of equations of state, since the thermodynamic state depends on additional parameters introduced by the enclosing surface. In this work, we present a consistent thermodynamic framework that represents an equation of state for pure, confined fluids. The total system is decomposed into a bulk phase in equilibrium with a surface phase. The equation of state is based on an existing, accurate
description of the bulk fluid, and uses Gibbs’ framework for surface excess properties to consistently incorporate contributions from the surface. We apply the equation of state to a Lennard-Jones spline fluid confined by a spherical surface with a Weeks-Chandler-Andersen wall-potential. The pressure and internal energy predicted from the equation of state are nearly within the accuracy of properties obtained directly from molecular dynamics simulations. We find that when the location of the dividing surface is chosen appropriately, the properties of highly curved surfaces can be predicted from those of a planar surface. The choice of dividing surface affects the magnitude of the surface excess properties and their curvature dependence, but the properties of the total system remain unchanged. The framework can predict the properties of confined systems with a wide range of geometries, sizes, inter-particle interactions and wall-particle interactions, and it is independent of ensemble. A targeted area of use is prediction of thermodynamic properties in porous media, for which a possible application of the framework is elaborated.