Nonadditive hard-sphere fluid mixtures: A simple analytical theory
  We construct a non-perturbative fully analytical approximation for the thermodynamics and the structure of nonadditive hard-sphere fluid mixtures. The method essentially lies in a heuristic extension of the Percus-Yevick solution for additive hard spheres. Extensive comparison with Monte Carlo simulation data shows a generally good agreement, especially in the case of like-like radial distribution functions. 
Riccardo Fantoni and Andr\'es Santos
cond-mat.soft cond-mat.stat-mech physics.chem-ph