Phase diagrams for a binary mixture confined in narrow slitlike pores with energetically heterogeneous walls from a lattice mean-field approach

We investigate the phase behaviour of binary symmetric lattice fluid, exhibiting partial demixing in slitlike pores with heterogeneous walls. The calculations are carried out assuming a cubic lattice with vacancies and a model for heterogeneity similar to that of Röcken and Tarazona (1996 J. Chem. Phys. 105 2034). We concentrate on the effects of surface heterogeneity on the scenarios for the phase transformations. It is shown that for wide enough pores a step-wise condensation occurs between demixed phases. For narrower pores the λ-line may cross the boundaries of the bridge phase and multiple critical end points appear. In such cases, at low temperatures the bridge phase formation occurs between demixed phases, at intermediate temperature it involves mixed and demixed phases and finally it becomes a transition between two demixed phases again.