Thermodynamics of the Coulomb lattice gas within the mean spherical approximation

Abstract The free energy of the classical two-component three-dimensional Coulomb lattice gas is derived in the explicit form within the mean spherical approximation. The model exhibits three important features: the onset of the condensation into the NaCl-like ordered phase, the critical point which is probably connected with condensation effects and the critical point of the “gas-liquid” type at the low concentration.