Application of density functional perturbation theory to pure fluid liquid-vapor interfaces

Common density functional theories often use the so-called mean-field appro ximation to the attractive term of the free energy, which is not accurate w hen compared with molecular dynamics simulations. We applied a modification of this attractive free energy term of a local density functional approach where an analytical representation of the radial distribution function is taken into account. A cutoff Lennard-Jones-12-6 potential, divided accordin g to the Weeks-Chandler-Andersen prescription, is used as the intermolecula r interaction force model. This density functional perturbation approach gi ves the correct phase quilibrium and predicts a surface tension in excellen t agreement with recent molecular dynamics simulations. The surface tension of some pure simple fluids is predicted from an intrinsic contribution, ob tained by the modified density functional perturbation theory, plus contrib utions due to capillary wave roughening of the surface. The respective Lenn ard-Jones potential parameters were obtained from fitting to saturated liqu id densities of the pure fluids. (C) 2000 American Institute of Physics. [S 0021-9606(00)71030-0].