Ab initio study of structure and stability of beryllium compounds

Abstract

The ab initio closed-shell SCF method, combined with the energy gradient technique, is applied to study the structures of the monomers and heavy atom bridged dimers of the monosubstituted beryllium hydrides: HBeX (X = BH 2, CH 3, NH 2, OH, F and Cl) and the BeX 2 (X = CH 3, F and Cl). The nature of the bridging BeX bond in the electron deficient group (X = BH 2 and CH 3) and the strong donor—acceptor group (X = NH 2, OH, F and Cl) differs from each other. The relationship between the dimerization energies and the type of bridging radicals is examined with and without electron correlation by using SDCI and MP3 methods. The electron correlation plays an important role in forming the electron deficient bridged dimers (X = H, BH 2 and CH 3) and Cl bridged dimer, but not so much in the other lone pair bridged dimers (X = NH 2, OH and F). The dimerization energy of Be(CH 3) 2 is estimated to be 18 kcal mol −1, which is compatible with the experimental value of ca. 24 kcal mol −1. The vibrational frequencies of the monomers and dimers of BeX 2 are evaluated and compared with the experimental data if it exists.