Cost-effective description of strong correlation: Efficient implementations of the perfect quadruples and perfect hextuples models.

  title={Cost-effective description of strong correlation: Efficient implementations of the perfect quadruples and perfect hextuples models.},
  author={Susi Lehtola and John A. Parkhill and Martin Head‐Gordon},
  journal={The Journal of chemical physics},
  volume={145 13},
Novel implementations based on dense tensor storage are presented for the singlet-reference perfect quadruples (PQ) [J. A. Parkhill et al., J. Chem. Phys. 130, 084101 (2009)] and perfect hextuples (PH) [J. A. Parkhill and M. Head-Gordon, J. Chem. Phys. 133, 024103 (2010)] models. The methods are obtained as block decompositions of conventional coupled-cluster theory that are exact for four electrons in four orbitals (PQ) and six electrons in six orbitals (PH), but that can also be applied to… 

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