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# 6.11.3 (dT) and (fT) corrections

(July 14, 2022)

Alternative inclusion of non-iterative $N^{7}$ triples corrections is described in Section 7.10.25. 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. 952 Piecuch P., Włoch M.
J. Chem. Phys.
(2005), 123, pp. 224105.

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!