Entropy and multi-particle correlations in two-dimensional lattice gases

We analyse the statistical entropy of two-dimensional lattice-gas models in terms of the contributions which arise from space correlations of increasi ng order. The "residual multiparticle entropy", defined as the contribution to the excess entropy that is associated with correlations involving more than two particles, is calculated for the Ising and Coulomb lattice gases. The thermodynamic behaviour of the residual multiparticle entropy is then d iscussed in relation to the phase diagram of the model and the existence of underlying signatures of order-disorder phase transitions is also investig ated.