A noniterative asymmetric triple excitation correction for the density-fitted coupled-cluster singles and doubles method: Preliminary applications

An efficient implementation of the asymmetric triples correction for the coupled-cluster singles and doubles [Lambda CCSD(T)] method [S. A. Kucharski and R. J. Bartlett, J. Chem. Phys. 108, 5243 (1998); T. D. Crawford and J. F. Stanton, Int. J. Quantum Chem. 70, 601 (1998)] with the density-fitting [DF-Lambda CCSD(T)] approach is presented. The computational time for the DF-Lambda CCSD(T) method is compared with that of Lambda CCSD(T). Our results demonstrate that the DF-Lambda CCSD(T) method provide substantially lower computational costs than Lambda CCSD(T). Further application results show that the Lambda CCSD(T) and DF-Lambda CCSD(T) methods are very beneficial for the study of single bond breaking problems as well as noncovalent interactions and transition states. We conclude that Lambda CCSD(T) and DF-Lambda CCSD(T) are very promising for the study of challenging chemical systems, where the coupled-cluster singles and doubles with perturbative triples method fails. Published by AIP Publishing.