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Title: A new approach to approximate equation-of-motion coupled cluster with triple excitations

Authors:
ORCiD logo [1];  [2]
  1. Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, USA
  2. Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1326117
Grant/Contract Number:
FG02-07ER15884
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 12; Related Information: CHORUS Timestamp: 2018-02-14 10:59:22; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Matthews, Devin A., and Stanton, John F.. A new approach to approximate equation-of-motion coupled cluster with triple excitations. United States: N. p., 2016. Web. doi:10.1063/1.4962910.
Matthews, Devin A., & Stanton, John F.. A new approach to approximate equation-of-motion coupled cluster with triple excitations. United States. doi:10.1063/1.4962910.
Matthews, Devin A., and Stanton, John F.. 2016. "A new approach to approximate equation-of-motion coupled cluster with triple excitations". United States. doi:10.1063/1.4962910.
@article{osti_1326117,
title = {A new approach to approximate equation-of-motion coupled cluster with triple excitations},
author = {Matthews, Devin A. and Stanton, John F.},
abstractNote = {},
doi = {10.1063/1.4962910},
journal = {Journal of Chemical Physics},
number = 12,
volume = 145,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4962910

Citation Metrics:
Cited by: 5works
Citation information provided by
Web of Science

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  • The novel multireference equation-of-motion coupled-cluster (MREOM-CC) approaches provide versatile and accurate access to a large number of electronic states. The methods proceed by a sequence of many-body similarity transformations and a subsequent diagonalization of the transformed Hamiltonian over a compact subspace. The transformed Hamiltonian is a connected entity and preserves spin- and spatial symmetry properties of the original Hamiltonian, but is no longer Hermitean. The final diagonalization spaces are defined in terms of a complete active space (CAS) and limited excitations (1h, 1p, 2h, …) out of the CAS. The methods are invariant to rotations of orbitals within their respectivemore » subspaces (inactive, active, external). Applications to first row transition metal atoms (Cr, Mn, and Fe) are presented yielding results for up to 524 electronic states (for Cr) with an rms error compared to experiment of about 0.05 eV. The accuracy of the MREOM family of methods is closely related to its favorable extensivity properties as illustrated by calculations on the O{sub 2}–O{sub 2} dimer. The computational costs of the transformation steps in MREOM are comparable to those of closed-shell Coupled Cluster Singles and Doubles (CCSD) approach.« less
  • A new formalism closely related to the Method of Moment of Coupled-Cluster equations (MMCC) is obtained by embedding approximate coupled cluster (CC) or equation-of-motion CC (EOMCC) formalism into the formalism which uses cluster or excitation operators defined by excitation operators of higher rank with respect to a given approximation. Non-iterative corrections due to triples to the CC / EOMCC with singles and doubles (CCSD / EOMCCSD) reveal structural similarities to the CCSD(T) corrections for the ground state. Linked to our QM/MM module in NWChem this new algorithm is used to study the excited-state potential surfaces of C1₂O molecule in gas-phasemore » and CC1₄ solution.« less
  • Ab initio molecular quantum mechanics has been applied to the unimolecular dissociation of H/sub 2/CO. Basis sets as large as triple zeta plus double polarization (TZ+2P) were used in conjunction with complete optimization of all stationary point geometries. The classical barrier height is predicted with the TZ+2P basis set to be 101.9 (SCF), 95.0 (CISD), 90.4 (CCSD), and 86.8 kcal/mol (CCSDT-1). With correction for zero-point vibrational energies, the activation energy is predicted to be 81.4 kcal/mol, in good agreement with experimental estimates.
  • Dynamic polarizabilities for open- and closed-shell molecules were obtained using coupled-cluster (CC) linear response theory with full treatment of singles, doubles and triples (CCSDT-LR) with large basis sets utilizing the NWChem software suite. Using four approximate CC methods in conjunction with augmented cc-pVNZ basis sets, we are able to evaluate the convergence in both many-electron and one-electron spaces. For systems with primarily dynamic correlation, the results for CC3 and CCSDT are almost indistinguishable. For systems with more static correlation, the PS(T) approximation [J. Chem. Phs. 127, 164105 (2007) performs better that CC3. Additionally, the PS(T) approach separates the triples contributionmore » to the poles of the response function from the triples amplitudes themselves, and demonstrates that the latter are less important than originally thought Lastly, our results show that the choice of reference (ROHF versus UHF) can have a significant impact on the accuracy of polarizabilities for open-shell systems.« less
  • In this paper we discuss the performance of the non-iterative State-Specific Mul- tireference Coupled Cluster (SS-MRCC) methods accounting for the effect of triply excited cluster amplitudes. The corrections to the Brillouin-Wigner and Mukherjee MRCC models based on the manifold of singly and doubly excited cluster amplitudes (BW-MRCCSD and Mk-MRCCSD, respectively) are tested and compared with the exact full configuration interaction results (FCI) for small systems (H2O, N2, and Be3). For larger systems (naphthyne isomers and -carotene), the non-iterative BW-MRCCSD(T) and Mk-MRCCSD(T) methods are compared against the results obtained with the single reference coupled cluster methods. We also report on themore » parallel performance of the non-iterative implementations based on the use of pro- cessor groups.« less