The spin-half Ising model has been used with remarkable success in describing magnetism and phase transition in magnetic materials. Likewise, the lattice gas model, which uses the spin-1 Ising model, was employed to investigate the phase transition in liquid-gas systems. In all the earlier lattice gas models, the kinetic energy of atoms occupying the various lattice sites were not considered for finding the equation of state. In this paper we use the Hamiltonian with kinetic energy and a modified equation of state is obtained. The isotherms of this model show the behavior of real gases at all pressures and they also exhibit phase transition.

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