Automatic active space selection for the similarity transformed equations of motion coupled cluster method

Dutta, Achintya Kumar; Nooijen, Marcel; Neese, Frank

doi:10.1063/1.4976130

Cited by 63 publications

(78 citation statements)

References 54 publications

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“…The process of selecting this active space has already been made automatic using a process based on configuration interaction singles averaged densities. 48 In the present study, the default value (0.01) is used for both the occupied (OTHRESH) and virtual (VTHRESH) active space selection thresholds, in all but one cases. For the system containing a tetrafluor-ethylene and an ethyene molecule separated at 3.5Å, both values are set to 0.001 to reach convergence with respect to the size of the active space.…”

Section: Computational Details 21 Excitation Energy Calculationsmentioning

confidence: 99%

A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

Kozma

Tajti

Démoulin

et al. 2020

Preprint

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There are numerous publications on benchmarking quantum chemistry methods for excited states. These studies rarely include Charge Transfer (CT) states although many interesting phenomena in e.g. biochemistry and material physics involve transfer of electron between fragments of the system. Therefore, it is timely to test the accuracy of quantum chemical methods for CT states, as well. In this study we ﬁrst suggest a set benchmark systems consisting of dimers having low-energy CT states. On this set, the excitation energy has been calculated with coupled cluster methods including triple excitations (CC3, CCSDT-3, CCSD(T)(a)* ), as well as with methods including full or approximate doubles (CCSD, STEOM-CCSD, CC2, ADC(2), EOM-CCSD(2)). The results show that the popular CC2 and ADC(2) methods are much more inaccurate for CT states than for valence states. On the other hand, CCSD seems to have similar systematic overestimation of the excitation energies for both valence and CT states. Concerning triples methods, the new CCSD(T)(a)* method including non-iterative triple excitations preforms very well for all type of states, delivering essentially CCSDT quality results.<br>

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Section: Computational Details 21 Excitation Energy Calculationsmentioning

confidence: 99%

A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

Kozma

Tajti

Démoulin

et al. 2020

Preprint

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“…Thus, not all elements in the SD block of

\overset{G}{true}

are zero, although one may hope that the coupling between active and inactive blocks is small, especially if the difference in orbital energies is large. This allows for the automatization of the STEOM active space selection procedure by using state averaged CIS natural orbitals with large occupation numbers . One caveat is that partitioning the orbital spaces into active and inactive parts leads to the loss of unitary invariance, but the impact of this is usually negligible or can be removed by computing more roots .…”

Section: Substantive Modificationsmentioning

confidence: 99%

“…This allows for the automatization of the STEOM active space selection procedure by using state averaged CIS natural orbitals with large occupation numbers . One caveat is that partitioning the orbital spaces into active and inactive parts leads to the loss of unitary invariance, but the impact of this is usually negligible or can be removed by computing more roots . Once

\overset{S}{true}

is obtained, the G SS block can diagonalized which is an operation that scales as O ( N 4 ).…”

Section: Substantive Modificationsmentioning

confidence: 99%

Single‐reference coupled cluster methods for computing excitation energies in large molecules: The efficiency and accuracy of approximations

Izsák

2019

WIREs Comput Mol Sci

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110

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While methodological developments in the last decade made it possible to compute coupled cluster (CC) energies including excitations up to a perturbative triples correction for molecules containing several hundred atoms, a similar breakthrough has not yet been reported for excited state computations. Accurate CC methods for excited states are still expensive, although some promising candidates for an efficient and accurate excited state CC method have emerged recently. This review examines the various approximation schemes with particular emphasis on their performance for excitation energies and summarizes the best state-of-the-art results which may pave the way for a robust excited state method applicable to molecules of hundreds of atoms.Among these, special attention will be given to exploiting the techniques of similarity transformation, perturbative approximations as well as integral decomposition, local and embedding techniques within the equation of motion CC framework. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Structure and Mechanism > Molecular Structures K E Y W O R D S accuracy, coupled cluster, efficiency, excited states, single reference | INTRODUCTIONIn their lucid review written a few years ago, 1 Sneskov and Christiansen discussed the various coupled cluster (CC) methods available for excited states. Using the systematic machinery of response theory, they described a hierarchy of methods, established a link between response theory and equation of motion (EOM) methods, and finished by discussing a number of approaches that might be used to reduce the computational cost. The present review aims at providing an overview of efficient methods available primarily for large molecules, and hence the emphasis will be laid more upon recent methodological advances which reduce the cost and on the extent this affects the accuracy of these methods. For ground state calculations, choosing a reference method for benchmarks is quite easy, since the CC singles doubles and perturbative triples, or CCSD(T), ansatz 2 is not only widely regarded as the gold standard of quantum chemistry, but it has also recently become possible to compute CCSD(T) energies for molecules containing several hundred atoms. 3 For excited states, progress has been

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“…The occupied index in the above equation is still in local basis, and one can perform a recanonicalization of the occupied space by diagonalizing the occupied‐occupied block of the Fock matrix. However, the recanonicalization is only important in active space‐based methods like STEOM‐CCSD, and the EOM‐CCSD energies are invariant to it. The advantage of this approach is that one uses a single set of PNOs for the entire calculation, because only the ground state calculation is performed in terms of PNOs and excited state is done in terms of the canonical orbitals.…”

Section: Theory and Computational Detailsmentioning

confidence: 99%

Bound anionic states of DNA and RNA nucleobases: An EOM‐CCSD investigation

Tripathi

Dutta

2018

Int J of Quantum Chemistry

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In this article, we have studied the bound anionic states of DNA and RNA nucleobases using the newly developed bt‐PNO‐EOM‐CCSD method and extended basis sets. All of the five nucleobases have a single bound anionic state, which is dipole bound in nature. The electron affinity corresponding to the dipole‐bound state is found to be extremely sensitive to the used basis set, and a proper agreement with the available experimental data requires a large basis set with a sufficient number of diffuse functions. Electron correlation plays a major role in stabilizing the bound anionic states of nucleobases. No valence‐bound anionic states are observed for any of the nucleobases.

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Automatic active space selection for the similarity transformed equations of motion coupled cluster method

Cited by 63 publications

References 54 publications

A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

Single‐reference coupled cluster methods for computing excitation energies in large molecules: The efficiency and accuracy of approximations

Bound anionic states of DNA and RNA nucleobases: An EOM‐CCSD investigation

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