Alternative inclusion of non-iterative triples corrections is described in Section 7.9.23. 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) and CR-CCSD(T) methods of Piecuch and coworkers.Piecuch:2005
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!