Application of the revised lattice density functional theory in slits

The lattice density functional theory (LDFT) was modified for monoatomic molecule adsorption systems in slits, and the revised mean field approximation and Gibbs-Helmholtz equation were introduced into the construction of Helmholtz function. Results of the revised model show a satisfactory consistence with that by Monte Carlo (MC) simulation, whereas the original LDFT data show a large deviation from it. It indicates that the mean field approximation will bring obvious system errors in the original LDFT. Multilevel adsorption occurs in slits, and different density profiles exist at a specific equilibrium concentration. This kind of multilevel adsorption is also clearly shown on the Gibbs isotherm. By comparison of results between the revised and the original LDFT, it is found that both of them can predict the multilevel adsorption behaviors, but there are still large differences between them.