Adsorption hysteresis and capillary condensation in disordered porous solids: a density functional study

TL;DR

This study uses a density functional approach to explore how fluids condense in disordered porous materials, revealing complex free-energy landscapes that cause hysteresis and metastability.

Contribution

It introduces a combined mean-field density functional and lattice-gas model to analyze both equilibrium and out-of-equilibrium capillary condensation in disordered media.

Findings

Capillary condensation involves complex free-energy landscapes with many metastable states.

Finite-size effects influence the presence of phase transitions.

Numerical methods effectively identify metastable states.

Abstract

We present a theoretical study of capillary condensation of fluids adsorbed in mesoporous disordered media. Combining mean-field density functional theory with a coarse-grained description in terms of a lattice-gas model allows us to investigate both the out-of-equilibrium (hysteresis) and the equilibrium behavior. We show that the main features of capillary condensation in disordered solids result from the appearance of a complex free-energy landscape with a large number of metastable states. We detail the numerical procedures for finding these states, and the presence or absence of transitions in the thermodynamic limit is determined by careful finite-size studies.