Spin-1 lattice-gas model. II. Condensation and phase separation in a binary fluid

Abstract
A spin-1 lattice-gas model is shown to describe condensation and phase separation in a binary fluid. The Ising-like Hamiltonian involves quadrupolar, dipolar, and crossed quadrupolar-dipolar interactions and is treated in the molecular-field approximation. Various experimental phase diagrams are reproduced qualitatively, exhibiting liquid-gas and liquid-liquid equilibrium lines, critical, azeotropic, and triple lines.