Calculation of the compressibility coefficient for a mixture of dense gases

The compressibility coefficients of simple gases and their mixtures are calculated within a modified lattice-gas model. It is demonstrated that, apart from the volume occupied by atoms and molecules of individual oases and the interactions of atoms in the quasi-chemical approximation allowing for the effects of short-range correlations, this model takes into account the three-particle interactions and excluded volume effects and offers a more accurate description of the behavior of the isotherms in the vicinity of the critical points in terms of calibration functions. It is shown that the modified lattice-gas model ensures a high accuracy of the calculations in the ranQes below and above the critical temperature. The calculated data OD the phase diagram of argon and the compressibility coefficients of individual gases and an Ar + N-2 mixture are compared with available experimental data. The concentration and temperature dependences of the effective energy of intermolecular interaction are discussed.