Sorption strains and their consequences for capillary condensation in nanoconfinement

Abstract

We employ Monte Carlo simulations in a semi-grand canonical ensemble to investigate the impact of pore deformation on capillary condensation in nanoconfined fluids. The fluid is composed of 'simple' spherically symmetric molecules of the Lennard-Jones type. These molecules are confined to a slit pore, where the pore walls consist of a single layer of atoms distributed according to the (100) plane of the face-centred cubic lattice. The atoms are bound to their equilibrium lattice sites by harmonic potentials such that they can depart to some extent from these sites on account of their thermal energy and the interaction with the fluid molecules. Under experimentally realistic conditions, our results show that, upon filling with fluid, the effective average pore size first increases, and then drops sharply at capillary condensation. The pore eventually expands again when the density of the confined liquid-like phase is further enhanced. Compared with the ideal case of perfectly rigid substrates, deformability of the pore causes capillary condensation to shift to higher bulk pressures; that is, the liquid-like phases are destabilised relative to the confined gas-like phases.

SANS investigations of CO2 adsorption in microporous carbon

“…As pressure increases, CO 2 molecules try to enter the pores leading to higher pore filling degree and densification. The solvation pressure depends on the pore width and fluid pressure and it increases with increasing fluid pressure and decreases with increasing pore width [51,52]. At pressure P/P sat~0 .3 the pore width exceeds twice the diameter of the CO 2 molecules.…”

Solid deformation induced by the adsorption of methane and methanol under sub- and supercritical conditions

“…They found that pores can both expand and contract, depending on the pore size and pressure of the adsorptive gas. Gunther and Schoen [26,27] have employed computer simulation to study the effects of the capillary condensation of simple L-J molecules on the behaviour of model deformable solids and also found that both expansion and contraction could occur as the adsorbate pressure moves through the transition region. Neimark and co-workers have used density functional theory to study methane and carbon dioxide adsorption in carbons under very high pressures as a model system for sequestration in coal seams [28,29].…”

Capillary condensation in deformable mesopores: wetting versus nanomechanics

“…In other words, κ is a measure of rigidity of the substrates. For values of κ used below we utilized a modified Lindemann criterion to ensure that over the temperature ranges studied the solid substrates do in fact not melt [30]. Hence, in the system of interest the total configurational energy may be expressed as [see Eqs.…”