Duh Haymet

The Duh-Haymet (Ref. 1) (1995) Padé (3/2) approximation for the Bridge function for the Lennard Jones system is (Eq. 13)

$B(\gamma ^{*})=-{\frac {1}{2}}\gamma ^{*2}\left[{\frac {1}{\left[1+\left({\frac {5\gamma ^{*}+11}{7\gamma ^{*}+9}}\right)\gamma ^{*}\right]}}\right]$

where (Eq. 10) $\gamma ^{*}(r)=\gamma (r)-\beta \Phi _{p}(r)$ where $\Phi _{p}(r)$ is the perturbative part of the pair potential (Note: in the WCA separation for the Lennard Jones system, the `perturbative part' is the attractive part).

References

1. Der-Ming Duh and A. D. J. Haymet "Integral equation theory for uncharged liquids: The Lennard-Jones fluid and the bridge function", Journal of Chemical Physics 103 pp. 2625-2633 (1995)