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.