Density Functional Theory for Studies of Multiple States of Inhomogeneous Fluids at Solid Surfaces and in Pores

Two new versions of the density functional theory (DFT), which correspond to the canonical ensemble and the Gibbs ensemble respectively, are applied to study multiple equilibrium states and associated hysteresis on examples of capillary condensation of argon in nanopores of MCM-41 mesoporous molecular sieves and Kr adsorption on carbon. The canonical ensemble DFT (CEDFT) allows us to trace not only the stable and the metastable states along the hysteresis loop, but also the unstable states inside the hysteresis loop. The Gibbs ensemble DFT (GEDFT) allows us to determine precisely the points of equilibrium phase transitions in confined fluids.