A simultaneous Eigen valued expression to model the three coupled electronic states with triply and doubly degenerate seams together I

Abstract

AbstractThe accurate modeling of triply and doubly degenerate seam together while computing the coupled multiple potential energy surfaces globally remains a challenging task due to the unavailability of a suitable model function taking care of this aspect. In this paper, we present such a function capable of predicting many‐fold electronic degeneracies simultaneously as well as the features found away from the vicinity of such degeneracies if present in the coupled surfaces disregarding the symmetry requirements. The basis of the proposed model comes from the analytical diagonalization of a real valued diagonally symmetric diabatic matrix and thus, the resulting three symbolic Eigen valued functions form the basis of model to be used in this work. From the analytical model, an attempt was made to provide an analytical expression for the adiabatic‐diabatic transformation angle. Few applications were considered starting from the simple physical model systems to actual realistic molecule illustrating how the present model function are being applied to them to show the presence of degeneracies among the three electronic states.