Energy hypersurface local properties of the O2HF- rearrangement

This work analyses a case where.Murrell's proposal, stating that a second-order point must lie above a first-order one, is apparently violated. Study at the SCF-UMP2 level within the D95 + + basis set, of one critical point of the O2HFanion, previously proposed to be of order two by Lopez, shows the importance of the electronic correlation. The critical point associated with the 21-1 state should rather be considered as a superposition of two first-order ones. The present analysis reveals that this contradistinction can be explained by three unconsidered elements: the local symmetry, the electronic correlation and the internal variables description.