The structure and energetics of B3N2, B2N3, and BN4: Symmetry breaking effects in B3N2

Abstract

The structures of B3N2, B2N3, and BN4 have been investigated using complete active space SCF (CASSCF) and augmented coupled cluster (CCSD(T)) methods. B3N2 has a symmetry-broken linear ground state structure BNBNB((2) Sigma(+)) and is very stable. B2N3 has a linear ground state structure BNBNN((II)-I-2) and is nearly isoenergetic with its (thermodynamically preferred but symmetry forbidden) dissociation products BNB((2) Sigma(+)) + N-2((1) Sigma(g)(+)). BN4 has the ground state structure NNBNN((IIu)-I-2) that is symmetry broken at the CCSD(T), but symmetric at the CASSCF level. Predictions for the infrared spectrum of the species involved have been given. The best computed total atomization energies Sigma D-e (error bar +/- 4 kcal mol(-1)) are: B3N2, 504.6 kcal mol(-1); B2N3, 479.1 kcal mol(-1); and BN4, 460.8 kcal mol(-1).