Calculation of phase diagram and the thermodynamic quantities by the Landau mean field model close to the solid - liquid and solid - solid transitions in n-paraffins

Abstract

We calculate the phase diagrams and predict the temperature dependence of the thermodynamic quantities at high pressures for the solid - liquid and solid - solid transitions in n-paraffins. This calculation is performed by fitting the phase line equations as obtainedfrom the Landau model to the experimental data from the literature. On thebasis of the Landau model, phase diagram of the solid - solid transition ispredicted at 0.1 MPa for the binary mixtures of n-tridecane + (n-hexane and cyclohexane).For the calculation of the heat capacity the extended mean field is employedfor the n-paraffins studied here. We find that our calculated phase diagrams explain the observed behaviour of the liquid - solid transitions at high pressures in those binary mixtures. Our phase diagrams predicted at 0.1 MPa and our predictions for the thermodynamic quantities can be compared with the experiments for those binary mixtures.