Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Département de Physique, Faculté des Sciences de Tunis, Université de Tunis-El Manar, Le Belvédère, 1060 Tunis, Tunisia.
J Chem Phys. 2012 Jan 14;136(2):024316. doi: 10.1063/1.3674164.
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.
采用大基组和包含完全活性空间自洽场、内收缩多参考组态相互作用、标准耦合簇（RCCSD(T)）方法以及新实现的显式关联耦合簇方法（RCCSD(T)-F12）在内的组态相互作用方法，对MgO(3)及其在分子和渐近区域的最低电子态的稳定异构体进行了精确的从头算计算。预测存在三种稳定形式：环状全局最小的 c-MgO(3)(+)，其次是准线性异构体 l2-MgO(3)(+)。还发现了具有 C(s)对称性的第三种异构体 l1-MgO(3)(+)。此外，我们沿着 R(MgO)和 R(OO)伸缩坐标计算了 MgO(3)的最低二重态和四重态电子态的六维势能面的一维切割，涵盖了分子和渐近区域。这些曲线后来用于讨论该阳离子的亚稳性，并提出 Mg(+) + O(3)大气重要离子-分子反应和相关反应通道的合理机制。
