THEORY OF GAS-GAS PHASE-TRANSITION IN RARE-GAS BINARY-MIXTURES

The lines of critical points of rare-gas binary mixtures are evaluated within the framework of a statistical mechanics theory of thermodynam ic stability, recently developed by Chen and Forstmann. The phase inst abilities an related to the local compositional and density order in t he fluid through a density functional expansion of the grand canonical potential. The structural inputs are determined by using the thermody namically self-consistent integral equation scheme known as hypernette d chain/mean spherical approximation (HMSA). A good agreement is obtai ned with neutron scattering data of He-Xe and Ne-Xe mixtures near the phase transition. Although the accuracy in reproducing the experimenta l critical point lines is only semi-quantitative, the qualitative beha viors are properly described. For the first time, a detailed microscop ic interpretation of the so called behavior of the ''second type'' of the critical line is given. (C) 1996 American Institute of Physics.