Scaled particle equation of state for hard non-spherical molecules

Applications of the method of anti-symmetrized product of strongly orthogonal geminals (APSG) to the boron hydrides B₂H₆, B₄H₄, B₄H₁₀, B₅H₉, B₅H₁₁ and B₆H₁₀ are described. Minimal basis sets of Slater-type orbitals are employed throughout. The APSG method is found to act as a localization process, with the B-H (terminal) and B-H (bridge)-B geminals well localized and transferable. Generation of several valence structures for B₅H₉, B₅H₁₁ and B₆H₁₀ suggests that the framework geminals of the preferred structure are of the closed three-centre type, although structures involving open BBB framework geminals are less stable by only a few kcal mol^-1. The principal natural orbital of each geminal is similar to the corresponding orbital produced by various localization criteria, while the weakly occupied natural orbitals are also localized and involve anti-bonding interactions between the component atoms of the bond.