ISOSPIN LATTICE-GAS MODEL AND NUCLEAR-MATTER PHASE-DIAGRAM AND PRESSURE-VOLUME ISOTHERMS

We study a cubic lattice gas model for nuclear matter where each latti ce site can be either occupied, by one proton or one neutron, or unocc upied. A nearest-neighbor interaction of the form - Sigma((ij)) J(ij)t au(zi)tau(zj) assumed. Our model is an isospin-1 Ising model, with tau (z) = (1, 0, -1) representing respectively (proton, vacancy, neutron). A kinetic-energy term has been included in our model. Under the Bragg -Williams mean-field approximation our model exhibits the existence of a dense phase (liquid-like) and a rare phase (gas-like). The nuclear- matter p-v isotherms given by our model are discussed.