An Excess Chemical Potential for Hard-Sphere Diatomic Liquid from Integral Equation Approach

The reference interaction site model (RISM) theory has been employed in the study of hard homonuclear and heteronuclear diatomic liquids. The RISM equation coupled with the Percus–Yevick and Martynov–Sarkisov closures has been solved numerically. The excess chemical potential has been computed using analytic expression based on correlation functions. An improved prediction of an excess chemical potential has been done with an interpolation scheme, which relates an excess chemical potential for hard-sphere fluid to that of tangent hard-sphere diatomic fluid at the same density. Our findings for an excess chemical potential for hard homonuclear fluid are compared with available accurate data. Maximum deviations of the excess chemical potential from the Percus–Yevick and Martynov–Sarkisov approximations are of \(9.56\%\) $9.56\%$ and of \(5.58\%\) $5.58\%$ , respectively. Some values of numerically obtained excess chemical potential for hard heteronuclear diatomic fluid present good comparison with available Monte Carlo data. To our knowledge, this is the first attempt to calculate an excess chemical potential for hard diatomic fluid in the Martynov–Sarkisov approximation. Moreover, radial distribution functions for hard-sphere, tangent hard homonuclear, and heteronuclear diatomic fluids from the Martynov-Sarkisov approximation are in good agreement with those in the literature.