SEARCH Articles Figures Tables CCSD CCSD -coupled clusters CCSD coupled-cluster singles, doubles approximations CCSD coupled-cluster singles, doubles calculations CCSD coupled-cluster singles, doubles triples, quadruples Cluster coupled Coupled cluster single double triple CCSD Coupled cluster single-double excitations CCSD) Coupled cluster singles and doubles (CCSD Coupled cluster singles and doubles CCSD) method Coupled-cluster doubles