Abstract

The equation-of-motion coupled-cluster method (EOM-CCSD) and its quadratic CI (EOM-QCISD) variant for excited states have been implemented in the ACES II program system. Results for open- and closed-shell reference states are reported for Be, N2, CO, O2, and O3. The results show that EOM-CCSD and EOM-QCISD generally provide reliable results for electronic excitation energies, particularly when the excited state is dominated by single excitations.