SURFACE-TENSION OF MIXTURES OF MOLECULAR FLUIDS - COMPARISON BETWEEN THE EXPERIMENTAL-STUDY AND THEORETICAL-STUDY OF CH4+KR, KY+NO, AND CH4+NO

We report a study of the surface tension of three binary liquid mixtur es of molecular fluids, A microscopic mean field theory (MFT) has been used to calculate the theoretical results enabling the comparison wit h the experimental data, The mean field theory has been successfully u sed in the prediction of the surface properties of simple systems comp osed by quasi-spherical molecules, In the present study the MFT was ab le to reproduce the essential features of the interfacial properties o f the systems CH4 + Kr, Kr + NO and CH4 + NO, The pure components were modelled by Lennard-Jones potentials with a set of intermolecular par ameters taken from the literature for Kr and calculated from the fitti ng of the energy parameters (epsilon) to the surface tension, for CH4 and NO. In the case of the mixtures, it was found that reasonable agre ement with experiment can only be obtained by allowing deviations from the Lorentz-Berthelot combining rules. For the CH4 + Kr system we use d the binary energy parameter xi obtained through a fitting to the bul k properties; for the Kr + NO and CH4 + NO systems the binary paramete r was adjusted to the interfacial properties. (C) 1997 Academic Press