Topological study, using a coupled ELF and catastrophe theory technique, of electron transfer in the Li+Cl2 system

Abstract

A topological study of electron transfer in the {Li+Cl₂} system, based on catastrophe theory and using ELF as a starting point, has been achieved. It enables the determination of the method-independent invariants that might be used for characterizing the well-documented harpooning process in all types of geometry. This study has shown that the process is characterized by an electron jump from the covalent {Li+Cl₂} state, stable at large separation distances, to the ionic charge transfer state {Li⁺+Cl₂^-}. The topological invariant associated with this behaviour is a dual cusp catastrophe, whose existence has been found at any level of calculation, that is, MP2, DFT and CASSCF. The latter catastrophe is mostly associated with the actual cleavage of the Cl₂^- species. Analysis of the topological parameters allows the actual regions of PES crossings, in any geometry, to be localized. Our results suggest that the dual cusp catastrophe characterizes the diabatic surface crossings that are subjacent in the classical adiabatic analysis of the overall reaction path.