Equations of state and contact values of hard-sphere radial distribution functions (rdf's) which are given by a linear combination of the Percus— Yevick and scaled-particle virial expressions are considered. In the one-component case the mixing coefficient
() is, in general, a function of the volume fraction
. In mixtures the coefficient
(
i
,
d
i
), in general, depends upon the volume fraction
i
, and diameter
d
i
, of each species,
i and
j. For the contact values
Y
ij
of the rdf's, the mixing coefficients
ij
(
k
) also depend on species
i and
j. Density expansions for the exact
for the one-component hard-sphere fluid are obtained and compared with several approximations made in earlier works and in our own work, as well as with simulations. For a mixture, it turns out that one cannot obtain the exact fourth virial coefficient by using a linear combination of the Percus-Yevick and scaled-particle virial expressions for
Y
ij
unless one allows
ij
to depend on mole fractions
x
i
even at the zeroth order of its density expansion. We also find that
ij
must depend on particle species
i and
j in order to satisfy the exact limits obtained earlier by Sung and Stell. A new equation of state for the binary hard-sphere mixture which satisfies all the exact limits we have considered is suggested.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.
相似文献