Calculation of coordination numbers for a three-component system with a pair interaction potential in the form of a rectangular well

Coordination numbers in a wide range of input parameters (reduced density, mixture composition, molecular size) were calculated in the Percus-Yevick a pproximation for ternary systems with rectangular-well interaction potentia ls. An exact analytic expression for distribution functions g(ab)(r) was us ed; the functions were represented as series in powers of density to second -order terms inclusive. The closest agreement with the results of Monte Car lo calculations was attained with distribution functions truncated after th e term first-order in density, which showed that the Mayer expansion poorly converged for the systems under consideration.