Dispersion truncation affects the phase behavior of bulk and confined fluids: Coexistence, adsorption, and criticality.

We present molecular simulations of bulk and confined Lennard-Jones fluids to assess the effect of dispersion truncation through a simple spherical cutoff. The latter is well corrected on a mean field level for bulk fluids if the cutoff distance is larger than about three molecular diameters. In confinement, however, there is no general analytical treatment, and thus, the truncated and shifted Lennard-Jones potential has to be employed, with drastic consequences on the bulk critical temperature, vapor/liquid coexistence pressure, and surface tension. We show using grand-canonical Monte-Carlo simulations of nitrogen adsorption in amorphous silica nanopores that the choice of the cutoff significantly modifies the pressure at which capillary condensation occurs and compute the capillary critical temperature in terms of a first order transition between an adsorbed film and filled pores.