Study of Topological Effects Concerning the Lowest A    and the Three A' States for the XXXX Ion.

@entity26 @entity3158 @entity72464
UNASSIGNED: A study of the topological effects, viz., the Jahn-Teller (JT) and @entity72464 ( @entity72464 ) effects, in CO2(+) has been carried out by calculating nonadiabatic coupling terms (NACTs) at the state-averaged CASSCF level using the cc-pVTZ basis set for the lowest three A' states and one A    state along a circular contour. Using the NACTs, the privileged adiabatic-to-diabatic transformation (ADT) angles (y12) for 1A' and 2A' states of @entity3158 (+) have been calculated along various circular contours. Employing one of the @entity26 atoms as the test particle exposed two conical intersections (ci) located on each side of the CO diatom. The main purpose of this study is to explore the possibility of forming reliable diabatic potential energy surfaces for this system. Success in achieving this goal is guaranteed by the ability to calculate quantized privileged ADT angles along closed contours covering large regions in configuration space (see, e.g., J. Phys. Chem. A 2014 , 118 , 6361 ). The calculations were carried out for two and three JT states. In most cases very nice quantization has been achieved although the calculations were frequently done, as required, for large regions in configuration space (sometimes >= 18   (2)). In one case, for which the quantization was not gratifying, the inclusion of the @entity72464 effect modified it considerably.
