Energy hypersurface local properties of the O2HF-1 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 O2HF- anion, previously proposed to be of order two by Lopez, shows the importance of the electronic correlation. The critical point associated with the (2)PI 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.