title: Symmetry breaking in the ground state of BNB: a high level multireference study.
abstract: A series of multireference approaches based on the SA-CASSCF wave function, i.e., CASPT2, MRCI, MRCI + Q, and MRAQCC with single- or multireference states, have been employed to investigate the symmetry breaking effect in the ground state X (2)Sigma(u)(+) of the triatomic BNB radical. We found that the mixing of the reference states contributes significantly to the dynamical correlation energy, which strongly affects the geometry of the ground state. Our results show that BNB in its ground state has a linear noncentrosymmetric structure with two equivalent global minima of the adiabatic potential energy surface and, respectively, two oppositely directed dipole moments of about 2 D. The barrier between the minima is about 20 cm(-1). The origin of the double-minimum potential in the ground state of BNB is explained as due to the pseudo-Jahn-Teller effect involving vibronic interaction with the first excited state A (2)Sigma(g)(+) via the asymmetric stretching vibrations.
authors.affiliation: Department of Chemistry and Biochemistry, Institute for Theoretical Chemistry, The University of Texas at Austin, Austin, Texas 78712-0165, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Wenli
authors.initials: W
authors.lastname: Zou
authors.forename: Isaac B
authors.initials: IB
authors.lastname: Bersuker
authors.forename: James E
authors.initials: JE
authors.lastname: Boggs