Phase behavior of lattice associating binary mixtures: A Monte Carlo study

The lattice gas model is used to study effects of molecular association on the phase behavior of binary symmetric mixtures, in which only dimers consisting of different particles can form. It is demonstrated that the increase of the association energy leads to qualitative changes of the phase diagrams. In particular, the demixing transition is observed only for sufficiently low association energy. That demixing transition can be either first order or continuous. For sufficiently high energy of association the condensed phase shows a very well ordered structure even at high temperatures.