Modern multireference methods and their application in transition metal chemistry

Khedkar, Abhishek; Roemelt, Michael

doi:10.1039/d1cp02640b

Cited by 32 publications

(31 citation statements)

References 196 publications

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“…The introduction of more efficient coupled cluster and multireference methods has provided exciting opportunities for computational applications to TM chemistry. [111,124,267,268] In multireference calculations of TM complexes, the size of the active space has been largely extended by the development of reduced-scaling methods such as DMRG, [30,31] FCIQMC, [32] and selected CI. [33][34][35][36] Explicitly correlated methods such as CCSD(T)-F12, [65,66] CASPT2-F12, [107] and NEVPT2-F12 [108] can be used to alleviate the basis set dependence.…”

Section: Conclusion and Outlooksmentioning

confidence: 99%

Ab Initio Methods in First‐Row Transition Metal Chemistry

Feldt

Phung

2022

Eur J Inorg Chem

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Molecules containing 3d transition metals (TMs) are usually associated with versatile reactivity, partly due to their complicated electronic structures involving multiple close‐lying spin states. An accurate description of different electronic states is notoriously difficult and still a challenge for computational methodologies. Density functional theory, although repeatedly shown to give less reliable results for near‐degeneracy problems, remains the workhorse to explore the reactivity of TM complexes. Ab initio wavefunction theory has been lagging behind due to its high computational cost. However, tremendous efforts have been put to improve their applicability over the past few years, particularly local coupled cluster and low‐scaling multireference methods. In this mini‐review, we highlight major advancements of these ab initio techniques and discuss their recent applications in the calculations of spin state energetics of first‐row TM complexes, ranging from spin crossover compounds and metalloproteins to biomimetic complexes capable of activating C−H bonds.

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Section: Conclusion and Outlooksmentioning

confidence: 99%

Ab Initio Methods in First‐Row Transition Metal Chemistry

Feldt

Phung

2022

Eur J Inorg Chem

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“…Here the last expression follows by multiplying out the numerator in (14), re-writing the term λ 2 Ψ (1) |H 0 |Ψ (1) as (1) , and using that Ψ (1) |H 0 − E 0 |Ψ (1) = −E (2) (since (H 0 −E 0 )R 0 is the identity on the orthogonal complement of Ψ 0 , to which H Ψ 0 belongs). By Taylor-expanding 1 over the denominator as 1 −…”

Section: B Error Scaling For Weakly Interacting Systemsmentioning

confidence: 99%

“…In light of tremendous progress in the past decade in transition metal chemistry [1][2][3], photosynthesis [4][5][6][7], single molecular magnets [8][9][10], and relativistic chemistry for compounds including heavy elements [11][12][13][14][15] the demand for a generally applicable method to efficiently treat strong electronic correlations and reveal solutions with chemical accuracy cannot be overemphasized. Although the main features of the electronic states are often characterized by the static correlations, contributions of an intractable number of high energy excited configurations with small weights, i.e., dynamical effects, can be crucial for an accurate theoretical description in light of experimental data [16,17].…”

Section: Introductionmentioning

confidence: 99%

Predicting the FCI energy of large systems to chemical accuracy from restricted active space density matrix renormalization group calculations

Friesecke¹,

Barcza²,

Legeza³

2022

Preprint

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We present a theoretical analysis and a new theory-based extrapolation method for the recently introduced restricted active space density matrix renormalization group (DMRG-RAS) method [arXiv:2111.06665] in electronic structure calculations. Large-scale numerical simulations show that our approach, DMRG-RAS-X, reaches chemical accuracy for challenging strongly correlated systems such as the Chromium dimer or dicarbon up to a large cc-pVQZ basis with moderate computational demands. The method is free of empirical parameters, performed robustly and reliably in all examples we tested, and has the potential to become a vital alternative method for electronic structure calculations in quantum chemistry, and more generally for the computation of strong correlations in nuclear and condensed matter physics.

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“…Full configuration interaction (Full‐CI) and selected configuration interaction (SCI) variants are frequently used in the context of multireference (MR) electronic structure theory which plays an important role in multiple branches of chemistry, for example, photochemistry and transition metal chemistry [1, 2]. Depending on the circumstances it is beneficial to solve the corresponding eigenvalue equation either in the basis of Slater determinants (SDs) or spin adapted configuration state functions (CSFs).…”

Section: Introductionmentioning

confidence: 99%

A recursive formulation of one‐electron coupling coefficients for spin‐adapted configuration interaction calculations featuring many unpaired electrons

Ugandi

Roemelt

2022

Int J of Quantum Chemistry

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This work reports on a novel computational approach to the efficient evaluation of one‐electron coupling coefficients as they are required during spin‐adapted electronic structure calculations of the configuration interaction type. The presented approach relies on the equivalence of the representation matrix of excitation operators in the basis of configuration state functions and the representation matrix of permutation operators in the basis of genealogical spin eigenfunctions. After the details of this connection are established for every class of one‐electron excitation operator, a recursive scheme to evaluate permutation operator representations originally introduced by Yamanouchi and Kotani is recapitulated. On the basis of this scheme we have developed an efficient algorithm that allows the evaluation of all nonredundant coupling coefficients for systems with 20 unpaired electrons and a total spin of S=0 within only a few hours on a simple Desktop‐PC. Furthermore, a full‐CI implementation that utilizes the presented approach to one‐electron coupling coefficients is shown to perform well in terms of computational timings for CASCI calculations with comparably large active spaces. More importantly, however, this work paves the way to spin‐adapted and configuration driven selected configuration interaction calculations with many unpaired electrons.

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Modern multireference methods and their application in transition metal chemistry

Abstract: Transition metal chemistry is a challenging playground for quantum chemical methods owing to the simultaneous presence of static and dynamic electron correlation effects in many systems. Wavefunction based multireference (MR)...

Cited by 32 publications

References 196 publications

Ab Initio Methods in First‐Row Transition Metal Chemistry

Ab Initio Methods in First‐Row Transition Metal Chemistry

Predicting the FCI energy of large systems to chemical accuracy from restricted active space density matrix renormalization group calculations

A recursive formulation of one‐electron coupling coefficients for spin‐adapted configuration interaction calculations featuring many unpaired electrons

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