Conical intersections in the H2CN molecule induced by the distortion from its Renner–Teller arrangement

Conical intersections (CIs) play a key role in nonadiabatic events. It was revealed, that the Renner effect in polyatomics is accompanied by symmetry-allowed CIs. Numerical and analytical results have demonstrated that two aligned CIs are formed in the molecular plane of the slightly bent C 2 H 2 + molecule. To some extent different results were obtained for the H2CN molecule. In order to fully and satisfactorily clarify this problem we calculated for the first time the Berry (topological) phase in this molecule for a single CI.