GEQUAC, an excess Gibbs energy model for simultaneous description of associating and non-associating liquid mixtures

A physically founded model for the excess Gibbs energy, GEQUAC (Group-surface Explicit QUAsiChemical theory), presented here, allows the description of associating as well as non-associating liquid mixtures. This is achieved by explicit accounting for the different poles of the molecular surface between which strong interactions take place in a mixture. The model is tested against results of Monte-Carlo computer simulations performed in lattice systems. Comparison of G(E), H-E and TSE determined from GEQUAC, computer simulations, and experiment shows that the thermodynamic behaviour of mixtures containing polar as well as hydrogen-bonding components can be modeled.