Vapour-liquid coexistence for purely repulsive point-Yukawa fluids

Using a simple mean-field theory and MC simulations we demonstrate the existence of a vapour-liquid transition in a fluid with purely repulsive Yukawa pair interactions and a density-dependent screening parameter. This transition does not fit into the classical Van der Waals picture, as the mechanism of liquid condensation is not caused by long-ranged attractions. The phase separation is, instead, driven by the enhanced screening at higher densities, which leads to ideal-gas behaviour at sufficiently high densities. A fluid at intermediate densities can thus reduce its free energy by separating into a dilute vapour and a high-density liquid.