Electron correlation effects on structural and cohesive properties of closo-hydroborate dianions (BnHn)2− (n = 5–12) and B4H4

Abstract

Results of ab initio and density functional calculations for the geometries and cohesive energies of the closo-hydroborate dianion series B_nH_n²⁻ (n = 5–12) and the hypothetical borane B₄H₄ are presented. The purpose of this contribution is three-fold: first we provide an in-depth comparison of the performance of a whole range of different quantum chemical standard methods ranging from Hartree–Fock over density functional theory and second-order many-body perturbation theory to the coupled-cluster method for the geometries. Second, we give quantitative insight into the relative stabilities of the various cluster compounds. Finally, we investigate approximations in ab initio calculations, making use of the locality of electron correlation in the occupied and virtual orbital spaces.