6.9 Non-Iterative Corrections to Coupled Cluster Energies

6.9.3 (dT) and (fT) corrections

Alternative inclusion of non-iterative N7 triples corrections is described in Section 7.8.21. These methods called (dT) and (fT) are of similar accuracy to other triples corrections. CCSD(dT) and CCSD(fT) are equivalent to the CR-CCSD(T)L and CR-CCSD(T)2 methods of Piecuch and coworkers.723

Note:  Due to a violation of orbital invariance, the (dT) correction can sometimes lead to spurious results. Therefore, its use is discouraged. Use (fT) instead!