Cavity Formation and the Drying Transition in the Lennard-jones Fluid

By simulation and theory, we study the probability of observing N molecular centers within molecular sized volumes for a Lennard-Jones fluid near liquid-vapor coexistence. For large volumes and small N, the probability distribution differs markedly from Gaussian. The free energy per unit surface area to form empty volumes (i.e., cavities) is a rapidly varying function of the radius for small cavities. It becomes constant for large volumes. The source of these behaviors is the occurrence of drying (i.e., solvent depletion) at the cavity surface. The crossover to drying occurs on microscopic length scales, with significant density depletion found for cavities with radii of the order of two or more Lennard-Jones diameters. Reasonable agreement is found between the simulation results and the theory developed by Lum, Chandler, and Weeks [J. Phys. Chem. B 103, 4570 (1999)].