The method of 2-point measures of molecular geometry is applied to the
calculation of the third virial coefficients of fluids of hard convex
molecules. For multicomponent fluids, existing semiempirical (SE) the
ories propose an expression in terms of the I-point measures volume V(
i), surface S(i), and integral mean curvature M(i) of the components i
= A, B, C. The method of 2-point measures does not introduce these qu
antities explicitly. In the limit of C either much smaller or much lar
ger than A and B, an expansion in the ratio of dimensions is obtained,
in which the leading terms are expressible in terms of the V(i), S(i)
, and M(i). For C small, the three leading terms are of this form; the
first two agree with the SE equations. For C large, only the leading
order is expressible in terms of the 1-point measures; it agrees with
the SE equations. The third virial coefficient is calculated numerical
ly for prolate and oblate spheroids using the method of 2-point measur
es. The infinite set of measures is truncated at the lowest possible l
evel required to yield exact results for hard spheres: all measures in
volving the curvature asymmetry are neglected. Results are compared wi
th existing exact values obtained by Monte Carlo integration, and with
the predictions of the SE theories.