Ornstein-Zernike equation for the convex molecule fluids

Pair distribution functions yield an important information on the structure of fluids. The general form of the Ornstein-Zernike equation which interre lates the total and direct correlation functions of molecular fluids, h(1, 2) and c(1, 2), respectively, is reformulated for systems of convex molecul es. An expression is derived which makes it possible to determine the avera ge correlation function as a sole function of the shortest surface-surface distance between hard cores of a pair of studied molecules. For both h and c, the shape effect is separated from the dependence of these functions on distance. As a result, the total correlation function can be determined fro m an expression, the convolution integral of which comprises the derivative of the cluster integral (related to the third virial coefficient) for thre e hard convex bodies. Preliminary results for the average correlation funct ion, g(av)(= h(av) + 1), in the system of hard prolate spherocylinders with the reduced core length L = 0.4 and packing fraction y = 0.3142 are presen ted; values of g(av) compare well with the corresponding simulation data.