Ab initio and model hypersurfaces for ground and excited state radical reactions

Abstract

A graphical representation of the potential energy hypersurfaces of the three-centre three-electron problem is proposed which is sufficient to fully describe the systerff/This method is used to visualize the hypersurfaces of the ground and the first excited doublet state of H3, obtained from VBCI calculations as well as from a judiciously parametrized HMO model and a semiempirical HL model. On the basis of these results three prototype radical reactions are discussed and the performance of the semiempirical models is assessed by comparison with the ab initio results, in order to see which features of the models are essential for a correct description of radical reactions. The importance of overlap within the MO approach and of electron interaction within the semiempirical HL method is thus revealed.