Interfacial phase transitions at solid-fluid and liquid-vapor interfaces

To study the interface between a solid surface and nitrogen vapor, the theo ry of Cahn was applied. The Peng-Robinson equation of state (PREOS) was inc orporated in the theory of Cahn to model the thermodynamic functions of the fluid. In this study the wetting transition, as earlier reported by Cahn, was shown. In addition, wetting transitions occurring at a liquid-vapor int erface of the three-phase LLV equilibrium of the binary mixtures hexane/wat er and benzene/water were examined. It was found that by making use of the gradient theory of van der Waals, in which the PREOS was incorporated, the transitions seem to be of third order. For the case where the PREOS was rep laced by the Associated-Perturbed-Anisotropic-Chain-Theory, no wetting regi on was found. II was argued that, in principle, it should he possible to mo del first-order welting transitions with the square gradient theory.