Electronic structure of the MgO 3+ cation

Accurate ab initio calculations are performed to investigate the stable isomers of MgO 3 and its lowest electronic states at both molecular and asymptotic regions. The calculations are done using large basis sets and configuration interaction methods including the complete active space self-consistent field, the internally contracted multi-reference configuration interaction, the standard coupled cluster (RCCSD(T)) approaches and the newly implemented explicitly correlated coupled cluster method (RCCSD(T)-F12). The presence of three stable forms is predicted: a cyclic global minimum c-MgO 3, which is followed by a quasi-linear isomer, l2-MgO 3. A third isomer of C s symmetry (l1-MgO 3) is also found. Moreover, we computed the one-dimensional cuts of the six-dimensional potential energy surfaces of the lowest doublet and quartet electronic states of MgO 3 along the R MgO and R OO stretching coordinates covering both the molecular and the asymptotic regions. These curves are used later for discussing the metastability of this cation and to propose plausible mechanisms for the Mg O 3 atmospherically important ion-molecule reaction and related reactive channels. © 2012 American Institute of Physics.This work has been supported by the PCI program of AECID-MAE of Spain, project PCI A/5107/06. M. L. Senent acknowledges the Ministerio de Educación of Spain for the grant (Grant No. AYA2008-00446 and for computing resources of CESGA. M.H. thanks a financial support from the PCMI program (INSU, CNRS).Peer Reviewe