On the virial expansion of model adsorptive systems

Abstract

We investigate the thermodynamic properties of various super-critical model adsorptive systems with different fluid–solid attractive strengths using the confined density virial expansion, with coefficients calculated using the Mayer-sampling Monte Carlo method up to fifth order. We find that the virial expansion converges for adsorptive systems over a density range corresponding approximately to the film-formation regime. Beyond this regime, higher-order effects become increasingly important. The virial expansion of the density profile is also investigated. It is determined that this expansion gives insight into the structure associated with adsorption. We also find that weakly attractive systems have a more negative second virial coefficient than strongly attractive systems. This runs counter to the usual interpretation of bulk fluid virial coefficients. This is due to the infinite-dilution limit being very different for adsorbed fluids compared to bulk fluids.

GRAPHICAL ABSTRACT

Keywords:

• Virial expansion
• confined fluids
• adsorption
• statistical mechanics
• thermophysical properties

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supporting Information

See Supporting Information for further details on the virial expansion, and results for other pore sizes not considered in main text.