“…However, due to the exponentially growing number of states, standard CI implementations are typically restricted to a small number of single-particle basis states or limited excitation degrees ͓e.g., single-double ͑SD-͒ CI and multireference-double-excitation ͑MRD-͒ CI͔. 23,25,26,29 As a generalization, the Monte Carlo CI ͑MCCI͒ has been introduced in Refs. 30 and 31, using an iterative optimization procedure by repeated Monte Carlo based configuration generation, diagonalization, and selection of the most important configurations.…”