Efficient implementations of the symmetric and asymmetric triple excitation corrections for the orbital-optimized coupled-cluster doubles (OCCD) method with the density-fitting approach, denoted by DF-OCCD(T) and DF-OCCD(T)Λ, are presented. The computational cost of the DF-OCCD(T) method is compared with that of the conventional OCCD(T). In the conventional OCCD(T) and OCCD(T)Λ methods, one needs to perform four-index integral transformations at each coupled-cluster doubles iterations, which limits its applications to large chemical systems. Our results demonstrate that DF-OCCD(T) provides dramatically lower computational costs compared to OCCD(T), and there are more than 68-fold reductions in the computational time for the C5H12 molecule with the cc-pVTZ basis set. Our results show that the DF-OCCD(T) and DF-OCCD(T)Λ methods are very helpful for the study of single bond-breaking problems. Performances of the DF-OCCD(T) and DF-OCCD(T)Λ methods are noticeably better than that of the coupled-cluster singles and doubles with perturbative triples [CCSD(T)] method for the potential energy surfaces of the molecules considered. Specifically, the DF-OCCD(T)Λ method provides dramatic improvements upon CCSD(T), and there are 8–14-fold reductions in nonparallelity errors. Overall, we conclude that the DF-OCCD(T)Λ method is very promising for the study of challenging chemical systems, where the CCSD(T) fails.
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21 September 2021
Research Article|
September 15 2021
Efficient implementations of the symmetric and asymmetric triple excitation corrections for the orbital-optimized coupled-cluster doubles method with the density-fitting approximation
Yavuz Alagöz
;
Yavuz Alagöz
Department of Chemistry, Hacettepe University
, Ankara 06800, Turkey
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Aslı Ünal
;
Aslı Ünal
Department of Chemistry, Hacettepe University
, Ankara 06800, Turkey
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Uğur Bozkaya
Uğur Bozkaya
a)
Department of Chemistry, Hacettepe University
, Ankara 06800, Turkey
a)Author to whom correspondence should be addressed: ugur.bozkaya@hacettepe.edu.tr
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a)Author to whom correspondence should be addressed: ugur.bozkaya@hacettepe.edu.tr
J. Chem. Phys. 155, 114104 (2021)
Article history
Received:
June 25 2021
Accepted:
August 29 2021
Citation
Yavuz Alagöz, Aslı Ünal, Uğur Bozkaya; Efficient implementations of the symmetric and asymmetric triple excitation corrections for the orbital-optimized coupled-cluster doubles method with the density-fitting approximation. J. Chem. Phys. 21 September 2021; 155 (11): 114104. https://doi.org/10.1063/5.0061351
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