EOM-CC guide to Fock-space travel: the C2 edition. (15th May 2019) - Gulania, Sahil
Abstract : Electronic structure calculations for C2, C2 −, and C2 2− using the CC/EOM-CC family of methods. Results illustrate that EOM-CCSD provides an attractive alternative to MR approaches. Abstract : Despite their small size, C2 species pose big challenges to electronic structure methods, owing to extensive electronic degeneracies and multi-configurational wave functions, which lead to a dense manifold of electronic states. We present detailed electronic structure calculations of C2, C2 −, and C2 2−, emphasizing spectroscopically relevant properties. We employ the double ionization potential (DIP) and ionization potential (IP) variants of the equation-of-motion coupled-cluster method with single and double substitutions (EOM-CCSD) and a dianionic reference state. We show that EOM-CCSD is capable of describing multiple interacting states in C2 and C2 − in an accurate, robust, and effective way. We also characterize the electronic structure of C2 2−, which is metastable with respect to electron detachment.