CASPT2 study on low-lying states of HBN and HNB radicals

In this study, some low-lying states of the HBN and HNB radicals have been studied using multiconfiguration second-order perturbation theory. The geometries of all stationary points along the potential energy surfaces (PESs) were optimized at the CASPT2/cc-pVQZ level. The ground and the first excited states of HBN were predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HNB is X2Σ+ state. The A2Π state of HNB has unique imaginary frequency, which was different from the previously published results. A bending local minimum M1 was found for the first time along the 12A″ PES, and the A2Π state of HNB should be the transition state of the isomerization reactions for M1 M1. The CASPT2/ANO potential energy curves (PECs) of isomerization reactions for HBN HNB were calculated as a function of HBN bond angle. By comparing the CASPT2 and CASSCF calculated results, we concluded that the influence of the dynamic electron correlation on HBN HNB system is not large. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011