Unified stability concept of mixed molecular lattices: random alloys or complexes

By using a pairwise-interaction approach in which homomolecular energies de pend on the composition, and heteromolecular energies on a long-range order parameter, a unified model able to explain the thermodynamic properties of random and ordered molecular alloys is obtained. The resulting Gibbs free energy describes both the asymmetry of mixing properties of random alloys a nd the coexistence of the immiscibility and long-range order through three independent parameters. The model is tested successfully in more than thirt y binaries belonging to aromatic or aliphatic families.