Phase diagrams and enthalpy calculation in a statistical model of binary mixtures

Abstract

The purpose of this work is to provide a comprehensive description of phase diagrams and heat evolution in binary mixtures. Our calculations are based on a spin-one Ising model and contain two order parameters. These order parameters are density and relative concentration and can describe the co-existence of phases with differing densities and compositions. We construct an appropriate thermodynamic potential for this model wih fixed values of externally manipulable parameters like pressure and relative composition. All the calculations are done using a mean field approximation. By varying just two parameters in the model, most of the elementary types of binary mixture phase diagrams can be generated. We compare our calculations of enthalpy with the features seen in the DSC (Differential Scanning Calorimetry) measurements on some organic binary mixtures and find them to be in good agreement.