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The article considers the main provisions of three versions of perturbation theory: BH (D. Henderson and J.A. Barker), WCA (J.D. Weeks, D. Chandler, and H.C. Andersen), and KLRR (H.S. Kang, C.S. Lee, T. Ree, and F.H. Ree) used to calculate the thermodynamic properties of binary mixtures of dense gases in a wide range of pressures and temperatures. The interaction of molecules is described using the spherically symmetric pair potential exp-6. Verification was carried out by comparing experimental data on the compression of binary helium–hydrogen and ammonia–hydrogen mixtures, as well as on shock-wave compression of liquid N2, O2 with the results of equilibrium thermodynamic calculations and Monte Carlo simulations. It is shown that for thermodynamic simulation of the properties of binary mixtures, the most accurate version of perturbation theory is the modernized KLRR-T theory. [ABSTRACT FROM AUTHOR]

A theoretical model of the equation of state of a two-component fluid with the exp-6 interaction potential has been developed. The model was created based on an improved version of perturbation theory. A technique for calculating the excessive Helmholtz energy of the two-component fluid is proposed. The technique is based on applying the Laplace transform for hard sphere distribution functions g( r); it considerably reduces time expenditures and increases the accuracy of calculations as compared to the technique that uses the functions g( r) directly. Based on the model proposed, the thermodynamic parameters of the two-component mixture of helium and hydrogen are calculated. To eliminate the problem of nonadditivity of hard sphere diameters and to obtain the best agreement of the calculated thermodynamic parameters with data of a computer experiment according to the Monte Carlo method, different schemes for separating the potential of interaction between helium atoms and hydrogen molecules into the reference and perturbing components were investigated. [ABSTRACT FROM AUTHOR]

The thermodynamic parameters of the two-component mixture of hydrogen atoms and molecules are calculated on the basis of perturbation theory with the use of the basic system of hard spheres. To eliminate the nonadditivity of hard sphere diameters and to obtain the best agreement of the calculated thermodynamic parameters with the Monte Carlo data, different schemes of subdivision of the interaction potential of hydrogen atoms and molecules into the basic and perturbing components are investigated. [ABSTRACT FROM AUTHOR]