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Stochastic analysis of capillary condensation in disordered mesopores

By Cedric J. Gommes and Anthony P. Roberts

Abstract

Most mesoporous materials of practical interest are inherently disordered, which has a significant impact on the condensation and evaporation of vapours in their pores. Traditionally, the effect of disorder is theoretically analyzed in a perturbative approach whereby slight elements of disorder (constriction, corrugation) are added to geometrically ideal pores. We propose an alternative approach, which consists of using a stochastic geometrical model to describe both the porous material and the condensate within the pores. This is done through a multiphase generalisation of the standard Gaussian random field model of disordered materials. The model parameters characterising the condensate provide a low-dimensional approximation of its configuration space, and we use a Derjaguin–Broekhoff–de Boer approximation to calculate the free-energy landscape. Our analysis notably questions the existence of vapour-like metastable states in realistically disordered mesoporous materials. Beyond capillary condensation, our general methodology is applicable to a broad array of confined phenomena

Topics: Density-functional theory, Small-angle scattering, Gaussian random-fields, Canonical Monte-Carlo, Nitrogen adsorption, Cylindrical pores, Porous-media, Phase-transitions, Mcm-41 materials, Model, 3100 Physics and Astronomy, 1606 Physical and Theoretical Chemistry
Publisher: 'Royal Society of Chemistry (RSC)'
Year: 2018
DOI identifier: 10.1039/c8cp01628c
OAI identifier: oai:espace.library.uq.edu.au:UQ:1ac18bb
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