Density profiles and solvation force for a liquid in a slit

Computer simulations and density functional theory results are reported for a Lennard-Jones liquid in a slit or pore formed by two parallel hard walls . Both density profiles and solvation forces are computed. Two classes of c alculation are performed. In the first class, a high bulk density is select ed and, starting from a high temperature, the temperature is reduced until the temperature corresponding to bulk liquid-vapour coexistence is reached. For small slit widths or exceedingly large widths, the density in the slit decreases continuously until the slit is virtually empty or 'dry'. When th e slit width is somewhat larger than a molecular diameter, but still finite , the density in the slit decreases continuously as the temperature is decr eased until there is an abrupt change in the density in the slit. Below thi s temperature, the density is smaller. Further decreases in the temperature , result in a continuous decrease in the slit density until the slit is vir tually empty. In the second class, the density and temperature for bulk coe xistence are chosen and the bulk density is increased. At the temperature a nd bulk density for bulk coexistence, the slit is virtually empty and remai ns so for all widths that we consider. As the bulk density is increased at constant temperature, the slit remains empty as the width is increased unti l some specific width is reached and then starts to fill abruptly. The agre ement of the density functional and simulation results is qualitative but g ood.