Equilibrium and out - of - equilibrium ( hysteretic ) behavior of Ñuids in disordered porous materials : Theoretical predictions
نویسندگان
چکیده
We study the relation between out-of-equilibrium (hysteretic) and equilibrium behavior in the capillary condensation of Ñuids in disordered mesoporous solids. Using mean-Ðeld density functional theory, we show that a simple lattice-gas model can reproduce the major experimental observations and that the classical van der Waals picture of metastability fails due the appearance of many metastable states. We Ðnd that (i) a true equilibrium capillary phase transition may occur when the perturbation induced by the solid is sufficiently small ; (ii) hysteresis does not necessarily imply the existence of this phase transition ; (iii) the disappearance of the hysteresis loop is not associated with capillary criticality ; and (iv) thermodynamic consistency is violated along the adsorptionÈdesorption isotherms.
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