Analytic studies of the hard dumbell fluid

We consider a closure to the site-site Ornstein-Zernike (SSOZ) equation that is solvable analytically in closed form and represents a considerable improvement over both the zero pole approximation and reference interaction site approximation for the hard dumbell fluid. The central idea is to add a Yukawa term to the functional form for the site-site direct correlation function outside the core region, the parameters of which are adjusted by thermodynamic and/or structural criteria. Numerical results using the simplest possible assignment scheme are reported.