Modelling adiabatic cusps in via 2 × 2 diabatic matrix

Abstract

An adiabatic model potential for the two lowest states of the ion with symmetry has been constructed by employing the combined hyperbolic inverse power representation (CHIPR) method. Three conical seams are involved, one arising for geometries with symmetry and two with . Modelling the cusps present in those geometries requires the use of the eigenvalue expression of a diabatic matrix as the fitting model in which the individual potentials are assumed to be pseudo-diabatic and modelled from pseudo-diabatic data points. Modelling the cusp greatly improves the accuracy of the overall fit in both states, well below for the ground and for the first excited electronic state. The loci of intersection in the analytical function so obtained match the ab initio ones with little deviation. Thermochemical properties extracted from the analytical function are also found to be in good agreement with available experimental results. GRAPHICAL ABSTRACT