The performance of a variety of density functional and ab initio methods on the structural problem of beryllium borohydride

Abstract

The D 2d and D 3d isomers of beryllium borohydride (BeB 2H 8) have been studied with different ab initio and density functional techniques. Optimized geometries were obtained with a polarized split valence basis set and electronic energies were calculated at the optimum geometry with an extended polarized basis set containing f functions. Both MP2 and MP4 calculations with the extended basis set indicate the D 3d conformer to be slightly more stable at the basis set level. The performance of many combinations of local and non-local exchange and correlation density functionals have been tested on this difficult structural problem. Only the non-local functionals approached the accuracy of ab initio MP2 calculations.