Bridging scales from molecular simulations to classical thermodynamics: densityfunctional theory of capillary condensation in nanopores

Abstract

With the example of the capillary condensation of Lennard-Jones fluid innanopores ranging from 1 to 10 nm, we show that the non-local densityfunctional theory (NLDFT) with properly chosen parameters of intermolecularinteractions bridges the scale gap from molecular simulations to macroscopicthermodynamics. On the one hand, NLDFT correctly approximates theresults of Monte Carlo simulations (shift of vapour–liquid equilibrium,spinodals, density profiles, adsorption isotherms) for pores wider thanabout 2 nm. On the other hand, NLDFT smoothly merges (above 7–10nm) with the Derjaguin–Broekhoff–de Boer equations which representaugmented Laplace–Kelvin equations of capillary condensation and desorption.