6.9.3 (dT) and (fT) corrections

Alternative inclusion of non-iterative $N^7$ triples corrections is described in Section 7.8.23. 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)${}_L$ and CR-CCSD(T)${}_2$ methods of Piecuch and coworkers.⁷³⁰

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!