PREWETTING AND DENSITY-FLUCTUATIONS IN THE PREWETTING SUPERCRITICAL PHASE

By means of Monte Carlo simulations, we investigate prewetting and its supercritical phase. First, we examine several fluid-substrate intera ction parameters, and discuss the general properties of prewetting. We locate a prewetting line for each parameter and obtain global phase d iagrams. Secondly, we study the prewetting supercritical phase, in whi ch density fluctuations in a film play an important role. From the str ucture factors of the first adsorption layer, we derive isotherms of t wo-dimensional compressibility and the extension of the prewetting lin e defined by mapping out the locus of points at which the compressibil ity attains its maximum value. It is shown that the prewetting line an d its extension bend one another at the prewetting critical point. Our results lend support to recent mercury-on-sapphire experiments.