Work

On the improvement of SPT2 approach in the theory of a hard sphere fluid in disordered porous media

Year: 2017

Type: article

Abstract: The SPT2 approach is based on the scaled particle theory and developed for the description of thermodynamic properties of hard sphere (HS) fluids in disordered porous media.Using this approach a porous medium is modelled as a quenched matrix of hard spheres (HS) or overlapping hard spheres (OHS).A hard sphere fluid immersed in a matrix can move in a void between matrix particles.A number of approximations were previously proposed within the SPT2 approach.Among these approximations, the SPT2b1 has been considered as the most successful and accurate one in a large range of fluid densities and for different matrix parameters.However, at high densities, it can lack accuracy, since it does not take into account that the maximum packing fraction of a HS fluid in a matrix is limited, not by the geometrical porosity of a matrix φ 0 and the probe particle porosity φ, but by another type of porosity φ * introduced in our previous studies.The porosity φ * is related to the maximal adsorption capacity of a matrix and it is lower than φ 0 and larger than φ.This can be crucial for a fluid in matrices of low porosities and at high fluid density, especially in the region near close-packing conditions.Therefore, the approximations SPT2b2 and SPT2b3 taking into account this feature were suggested, although they still needed a correction because of their poor accuracy.In the present study, we improved the versions of these approximations, named as SPT2b2 * and SPT2b3 * .We compare these different approximations with the results of computer simulations performed in the Monte Carlo grand-canonical ensemble.We test the SPT2 approach both for the one-and three-dimensional cases.We show that the SPT2b3 * provides a very good description of the chemical potential of a confined fluid, which is better than others.This extends the applicability of the SPT2 approach to the studies of very dense fluids confined in disordered matrices.

Source: Condensed Matter Physics

DOI: 10.5488/cmp.20.33602

Authors: Holovko, Patsahan, Dong

Institutions: Yukhnovskii Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, École Normale Supérieure de Lyon, Centre National de la Recherche Scientifique, Laboratoire de Chimie

Language: English

Topic: Phase Equilibria and Thermodynamics

Subfield: Physical and Theoretical Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: diamond

Funder: European Commission

Awards: G434337789, Effects of confinement on inhomogeneous systems