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  Reconciling Local Coupled Cluster with Multireference Approaches for Transition Metal Spin-State Energetics

Drosou, M., Mitsopoulou, C. A., & Pantazis, D. A. (2022). Reconciling Local Coupled Cluster with Multireference Approaches for Transition Metal Spin-State Energetics. Journal of Chemical Theory and Computation, 18(6), 3538-3548. doi:10.1021/acs.jctc.2c00265.

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 Creators:
Drosou, Maria1, Author
Mitsopoulou, Christiana A.1, Author
Pantazis, Dimitrios A.2, Author           
Affiliations:
1Inorganic Chemistry Laboratory, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 15771, Greece, ou_persistent22              
2Research Group Pantazis, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541711              

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 Abstract: Spin-state energetics of transition metal complexes remain one of the most challenging targets for electronic structure methods. Among single-reference wave function approaches, local correlation approximations to coupled cluster theory, most notably the domain-based local pair natural orbital (DLPNO) approach, hold the promise of bringing the accuracy of coupled cluster theory with single, double, and perturbative triple excitations, CCSD(T), to molecular systems of realistic size with acceptable computational cost. However, recent studies on spin-state energetics of iron-containing systems raised doubts about the ability of the DLPNO approach to adequately and systematically approximate energetics obtained by the reference-quality complete active space second-order perturbation theory with coupled-cluster semicore correlation, CASPT2/CC. Here, we revisit this problem using a diverse set of iron complexes and examine several aspects of the application of the DLPNO approach. We show that DLPNO-CCSD(T) can accurately reproduce both CASPT2/CC and canonical CCSD(T) results if two basic principles are followed. These include the consistent use of the improved iterative (T1) versus the semicanonical perturbative triple corrections and, most importantly, a simple two-point extrapolation to the PNO space limit. The latter practically eliminates errors arising from the default truncation of electron-pair correlation spaces and should be viewed as standard practice in applications of the method to transition metal spin-state energetics. Our results show that reference-quality results can be readily achieved with DLPNO-CCSD(T) if these principles are followed. This is important also in view of the applicability of the method to larger single-reference systems and multinuclear clusters, whose treatment of dynamic correlation would be challenging for multireference-based approaches.

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Language(s): eng - English
 Dates: 2022-03-162022-05-182022-06-14
 Publication Status: Published in print
 Pages: 11
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/acs.jctc.2c00265
 Degree: -

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Title: Journal of Chemical Theory and Computation
  Other : J. Chem. Theory Comput.
Source Genre: Journal
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Publ. Info: Washington, D.C. : American Chemical Society
Pages: - Volume / Issue: 18 (6) Sequence Number: - Start / End Page: 3538 - 3548 Identifier: ISSN: 1549-9618
CoNE: https://pure.mpg.de/cone/journals/resource/111088195283832