The coupled-cluster single, double, and triple excitation model for open-shell single reference functions

Abstract
The CCSDT model for general single determinant reference functions for open and closed‐shell electronic states has been implemented for the first time and has been used to compute the electron affinity of the F atom, the CH2, 3B11A1 energy difference, and the ionization potentials of 1A1 CH2. The results compare very well with FCI and are markedly superior to those of simpler coupled‐cluster methods.