Description of C2 dissociation using a naive treatment of dynamical correlation in the presence of quasidegeneracy of varying degree

Abstract

To obtain even qualitatively correct results of potential energy surfaces (PESs) of the ground and two lowest-lying excited singlet states of C2 is a difficult task due to the strong geometry-dependent closeness of these PESs leading to real and avoided crossings. Our IVO-SSMRPT method in which the nondynamical correlation is simplified with IVO-CASCI has been applied to these states. IVO-SSMRPT provides comparable results with reference theoretical and experimental data indicating all components of the approach work in harmony for a correct representation of the surfaces including the locations of the challenging crossing points between the states.