Molecular simulation of phase coexistence in adsorption in porous solids

In this work a recently proposed method, the gauge-cell Gibbs ensemble Monte Carlo, is extended to deal with polar substances. The behaviour of water, a hydrogen bonding, weakly adsorbing fluid, is compared with that of methane, a strongly adsorbing, non-polar fluid, in the vicinity of the phase transition. The mechanisms of condensation for the two species are seen to be significantly different in nature. A systematic study of the effect of the pore width on the phase equilibrium of water is also performed. Our results show that the narrowing of the pore shifts the equilibrium transition pressure to lower values and reduces the extent of vapour metastability, but exerts little influence on the stability of the liquid phase.