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arxiv: 2604.13009 · v2 · submitted 2026-04-14 · ⚛️ physics.chem-ph

EOM-fpCCSD: An Accurate Alternative to EOM-CCSD for Doubly Excited and Charge-Transfer States

Katharina Boguslawski , Pawe{\l} Tecmer This is my paper

Pith reviewed 2026-05-10 13:35 UTC · model grok-4.3

classification ⚛️ physics.chem-ph
keywords equation-of-motion coupled-clusterdoubly excited statescharge-transfer statespCCD referenceexcitation energiesQUEST databasecomputational chemistry
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0 comments X

The pith

EOM-fpCCSD using a frozen-pair pCCD reference yields more accurate and convergent excitation energies for doubly excited states than standard EOM-CCSD.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper introduces EOM-fpCCSD as an equation-of-motion method that starts from a frozen-pair pCCD reference wavefunction rather than a Hartree-Fock determinant. The approach aims to keep the computational cost low while adding enough dynamical correlation to handle excited states reliably. Benchmarks on charge-transfer states from the QUEST database produce energies close to those of EOM-CCSD, along with similar descriptions of directed charge flow when localized pCCD natural orbitals are used. The clearest gains appear for doubly excited states, where EOM-fpCCSD agrees better with theoretical best estimates than either EOM-CCSD or its pair-tailored variant and converges for several cases that defeat the other two methods. Readers would care because doubly excited states appear in many photochemical processes yet remain difficult to describe accurately with conventional single-reference tools.

Core claim

EOM-fpCCSD produces excitation energies for doubly excited states that lie closer to theoretical best estimates than those from EOM-CCSD or EOM-ptCCSD, while also converging for states that cause the standard methods to fail.

What carries the argument

EOM-fpCCSD, the equation-of-motion extension applied to a frozen-pair pCCD reference that supplies a compact description of static correlation before dynamical effects are restored.

If this is right

  • For charge-transfer excitations, EOM-fpCCSD energies stay close to EOM-CCSD and theoretical best estimates.
  • Directed charge-transfer character remains nearly identical across EOM-fpCCSD, EOM-CCSD, and EOM-ptCCSD when pCCD natural orbitals are employed.
  • Accuracy for doubly excited states improves relative to theoretical best estimates and convergence succeeds where the other two methods fail.
  • Both canonical Hartree-Fock and pCCD natural orbital bases can be used, with only minor effects on qualitative features such as charge-transfer character.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The reduced cost of the pCCD reference could extend reliable excited-state calculations to molecules larger than those accessible with full EOM-CCSD.
  • The improved behavior on doubly excited states may reflect better capture of static correlation effects that single-reference references miss.
  • Testing the same reference choice on transition moments or non-adiabatic couplings would show whether the energy gains carry over to other observables.

Load-bearing premise

The frozen-pair pCCD reference already contains enough correlation that the subsequent EOM correction step produces excitation energies free of large systematic errors for doubly excited and charge-transfer states.

What would settle it

A calculation on one of the QUEST doubly excited states that converges with EOM-fpCCSD but yields an excitation energy farther from the theoretical best estimate than the corresponding EOM-CCSD value.

read the original abstract

We introduce a new equation-of-motion coupled-cluster method based on a pair coupled-cluster doubles (pCCD) reference, termed frozen-pair EOM-CCSD (EOM-fpCCSD). This approach combines the computational efficiency of the pCCD ansatz with a dynamical correlation correction, enabling a reliable description of electronically excited states within the EOM framework. The method has been implemented in the open-source PyBEST software package. Its performance is systematically benchmarked against standard EOM-CCSD and its pair-tailored variant (EOM-ptCCSD), using both canonical Hartree-Fock and pCCD natural orbitals. For charge-transfer (CT) excitations taken from the QUEST database, EOM-fpCCSD yields excitation energies very close to those of EOM-CCSD, outperforming EOM-ptCCSD, as well as to the theoretical best estimates (TBEs). Working within the localized pCCD natural orbital basis allows us to determine the directed CT character, which quantifies the directed charge flow from one molecular domain to another. Numerical results show that EOM-fpCCSD, EOM-CCSD, and EOM-ptCCSD provide nearly identical descriptions of the directed CT character, despite changes in excitation energies. The true advantage of EOM-fpCCSD becomes evident for the challenging QUEST subset of doubly excited states. While EOM-ptCCSD performs similarly to standard EOM-CCSD, EOM-fpCCSD significantly outperforms both methods for these problematic states compared to TBEs. In addition to improving the accuracy of excitation energies, EOM-fpCCSD also converges for several states that standard EOM-CCSD and EOM-ptCCSD fail to converge. These results demonstrate that EOM-fpCCSD offers a promising and computationally efficient route toward a more accurate description of complex electronic excitations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript introduces EOM-fpCCSD, an equation-of-motion coupled-cluster method that employs a frozen-pair pCCD reference (with optional pCCD natural orbitals) as the starting point for the EOM-CCSD-like operator. It is implemented in PyBEST and benchmarked on charge-transfer excitations and the doubly excited subset from the QUEST database. The central claims are that EOM-fpCCSD yields CT excitation energies close to EOM-CCSD (and superior to EOM-ptCCSD) while matching TBEs, provides nearly identical directed CT character, and significantly improves both accuracy relative to TBEs and convergence for doubly excited states where EOM-CCSD and EOM-ptCCSD fail.

Significance. If the performance claims hold after addressing reference-quality analysis, EOM-fpCCSD would constitute a useful, lower-cost route to reliable excitation energies for doubly excited and charge-transfer states, where standard EOM-CCSD often struggles with convergence or accuracy. The open-source implementation and the use of pCCD natural orbitals to quantify directed CT character are concrete strengths that could facilitate adoption in computational chemistry workflows.

major comments (2)
  1. [Results (doubly excited states) and Methodology] The abstract and results on doubly excited states claim that EOM-fpCCSD significantly outperforms EOM-CCSD and EOM-ptCCSD relative to TBEs and converges for states where the others fail. However, no direct comparison is provided of the ground-state correlation energy recovered by pCCD versus canonical CCSD on the same QUEST molecules (or even a subset). This comparison is load-bearing because pCCD recovers only pair correlations; without it, the reported improvement cannot be distinguished from differential error cancellation between reference and EOM step.
  2. [Results (convergence behavior)] The convergence advantage is presented as a key practical benefit, yet the manuscript does not specify the number of states that fail to converge in EOM-CCSD/EOM-ptCCSD, the molecules involved, the residual-norm thresholds employed, or the maximum iteration counts. These details are required to assess whether the improvement is systematic or limited to a few outliers.
minor comments (2)
  1. [Abstract and CT results] The abstract states that EOM-fpCCSD, EOM-CCSD, and EOM-ptCCSD give 'nearly identical' directed CT character; a quantitative metric (e.g., mean absolute deviation or maximum deviation across the CT set) would make this statement precise.
  2. [Theory/Methodology] Clarify the precise definition of the 'frozen-pair' approximation within the EOM operator (e.g., which amplitudes are frozen and how the similarity-transformed Hamiltonian is constructed) to allow independent reproduction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their positive overall assessment and for the constructive comments that will help strengthen the manuscript. We address each major comment in detail below.

read point-by-point responses

  1. Referee: [Results (doubly excited states) and Methodology] The abstract and results on doubly excited states claim that EOM-fpCCSD significantly outperforms EOM-CCSD and EOM-ptCCSD relative to TBEs and converges for states where the others fail. However, no direct comparison is provided of the ground-state correlation energy recovered by pCCD versus canonical CCSD on the same QUEST molecules (or even a subset). This comparison is load-bearing because pCCD recovers only pair correlations; without it, the reported improvement cannot be distinguished from differential error cancellation between reference and EOM step.

    Authors: We agree that a direct comparison of ground-state correlation energies is valuable for interpreting the source of the observed improvements in excitation energies. Since EOM-CCSD calculations were already performed on the same QUEST molecules, the canonical CCSD correlation energies are available, and we have also computed the pCCD correlation energies. In the revised manuscript we will add a table (or supplementary section) reporting the percentage of correlation energy recovered by pCCD relative to CCSD for the doubly excited states subset. This will allow readers to assess whether the EOM-fpCCSD gains arise primarily from the reference or from the subsequent EOM step. revision: yes

  2. Referee: [Results (convergence behavior)] The convergence advantage is presented as a key practical benefit, yet the manuscript does not specify the number of states that fail to converge in EOM-CCSD/EOM-ptCCSD, the molecules involved, the residual-norm thresholds employed, or the maximum iteration counts. These details are required to assess whether the improvement is systematic or limited to a few outliers.

    Authors: We acknowledge that the current manuscript lacks these quantitative details. In the revised version we will add a dedicated paragraph and a small table listing: (i) the exact number of states (out of the QUEST doubly excited subset) that failed to converge for EOM-CCSD and EOM-ptCCSD, (ii) the specific molecules involved, (iii) the residual-norm threshold used (10^{-6}), and (iv) the maximum number of iterations allowed (50). This information will demonstrate that the convergence improvement with EOM-fpCCSD is systematic rather than limited to isolated cases. revision: yes

Circularity Check

0 steps flagged

No circularity: benchmarks against independent TBEs and external methods

full rationale

The paper introduces EOM-fpCCSD as a defined combination of a pCCD reference with an EOM operator and reports its numerical performance on the QUEST database. All accuracy claims are obtained by direct comparison to external theoretical best estimates (TBEs) and to independently implemented methods (EOM-CCSD, EOM-ptCCSD). No equation, parameter, or result is shown to be fitted to the target excitation energies or to reduce by construction to a self-defined quantity. Self-citations to prior pCCD work, if present, are not load-bearing for the reported excitation-energy improvements, which rest on external validation rather than internal redefinition.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the pCCD frozen-pair approximation being sufficient for EOM excited-state calculations; no new physical entities are postulated and no free parameters are explicitly fitted in the abstract.

axioms (1)
  • domain assumption The frozen-pair pCCD reference provides an adequate starting point for reliable EOM excited-state calculations
    This is the core approximation enabling both efficiency and the reported accuracy gains.

pith-pipeline@v0.9.0 · 5654 in / 1200 out tokens · 80035 ms · 2026-05-10T13:35:41.277508+00:00 · methodology

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Reference graph

Works this paper leans on

97 extracted references · 97 canonical work pages · cited by 1 Pith paper

  1. [1]

    D. J. Rowe,Rev. Mod. Phys., 1968,40, 153–166

    work page 1968

  2. [2]

    Geersten, M

    J. Geersten, M. Rittby and R. J. Bartlett,Chem. Phys. Lett., 1989,164, 57–62

    work page 1989

  3. [3]

    J. F. Stanton and R. J. Bartlett,J. Chem. Phys., 1993,98, 7029–7039

    work page 1993

  4. [4]

    R. J. Bartlett,WIREs Comput. Mol. Sci., 2012,2, 126–138

    work page 2012

  5. [5]

    Musiał,Quantum Chemistry and Dynamics of Excited States: Methods and Applications, 2020, 77–108

    M. Musiał,Quantum Chemistry and Dynamics of Excited States: Methods and Applications, 2020, 77–108

    work page 2020

  6. [6]

    Pathak, B

    H. Pathak, B. Sahoo, B. Das, N. Vaval and S. Pal,Phys. Rev. A, 2014,89, 042510

    work page 2014

  7. [7]

    A. Shee, T. Saue, L. Visscher and A. S. P. Gomes,J. Chem. Phys., 2018,149, 174113

    work page 2018

  8. [8]

    McClain, Q

    J. McClain, Q. Sun, G. K.-L. Chan and T. C. Berkelbach,J. Chem. Theory Comput., 2017,13, 1209–1218

    work page 2017

  9. [9]

    E. A. Vo, X. Wang and T. C. Berkelbach,J. Chem. Phys., 2024,160, 044106

    work page 2024

  10. [10]

    S. A. Kucharski, M. Włoch, M. Musiał and R. J. Bartlett,J. Chem. Phys., 2001,115, 8263–8266

    work page 2001

  11. [11]

    Kowalski and P

    K. Kowalski and P. Piecuch,J. Chem. Phys., 2001,115, 643–652

    work page 2001

  12. [12]

    Kowalski and P

    K. Kowalski and P. Piecuch,J. Chem. Phys., 2004,120, 1715–1738

    work page 2004

  13. [13]

    Kowalski, S

    K. Kowalski, S. Krishnamoorthy, O. Villa, J. R. Hammond and N. Govind,J. Chem. Phys., 2010,132, 154103

    work page 2010

  14. [14]

    Shen and P

    J. Shen and P. Piecuch,J. Chem. Theory Comput., 2012,8, 4968–4988

    work page 2012

  15. [15]

    D. A. Matthews and J. F. Stanton,J. Chem. Phys., 2016,145, 124102

    work page 2016

  16. [16]

    J. F. Stanton and J. Gauss,J. Chem. Phys., 1995,103, 1064–1076

    work page 1995

  17. [17]

    R. H. Myhre, A. M. Sánchez de Merás and H. Koch,J. Chem. Phys., 2014,141, 224105

    work page 2014

  18. [18]

    A. K. Dutta, M. Nooijen, F. Nesse and R. Izsák,J. Chem. Theory Comput., 2006,14, 72–91

    work page 2006

  19. [19]

    S. D. Folkestad and H. Koch,J. Chem. Theory Comput., 2020,16, 6869–6879. 0a Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland. E-mail: k.boguslawski@umk.pl 0b Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University ...

    work page 2020

  20. [20]

    Tuckman and E

    H. Tuckman and E. Neuscamman,J. Phys. Chem. Lett., 2025,16, 7889–7897

    work page 2025

  21. [21]

    Zhang, J

    H. Zhang, J. Zou, X. Ren and S. Li,J. Phys. Chem. Lett., 2025,16, 4635–4642

    work page 2025

  22. [22]

    J. Lin, X. Ren, H. Zhang, W. Li and S. Li,J. Phys. Chem. Lett., 2026,17, 3316–3324

    work page 2026

  23. [23]

    P. G. Szalay, T. Muller, G. Gidofalvi, H. Lischka and R. Shepard,Chem. Rev., 2012,112, 108–181

    work page 2012

  24. [24]

    B. Roos, P. Taylor and P. Siegbahn,Chem. Phys., 1980,48, 157–173

    work page 1980

  25. [25]

    Andersson, P.-A

    K. Andersson, P.-A. Malmqvist, B. O. Roos, A. J. Sadlej and K. Woliński,J. Phys. Chem., 1990,94, 5483–5488

    work page 1990

  26. [26]

    Andersson, P.-A

    K. Andersson, P.-A. Malmqvist and B. O. Roos,J. Chem. Phys., 1992,96, 1218–1226

    work page 1992

  27. [27]

    Pulay,Int

    P. Pulay,Int. J. Quantum Chem., 2011,111, 3273–3279

    work page 2011

  28. [28]

    Kozma, A

    B. Kozma, A. Tajti, B. Demoulin, R. Izsák, M. Nooijen and P. G. Szalay,J. Chem. Theory Comput., 2020,16, 4213–4225

    work page 2020

  29. [29]

    P.-F. Loos, M. Boggio-Pasqua, A. Blondel, F. Lipparini and D. Jacquemin,J. Chem. Theory Comput., 2025,21, 8010–8033

    work page 2025

  30. [30]

    Tuckman and E

    H. Tuckman and E. Neuscamman,J. Chem. Theory Comput., 2024,20, 2761–2773

    work page 2024

  31. [31]

    Tuckman, Z

    H. Tuckman, Z. Ma and E. Neuscamman,J. Chem. Theory Comput., 2025,21, 3993–4005

    work page 2025

  32. [32]

    Zheng, N

    Z. Zheng, N. R. Tummala, Y.-T. Fu, V. Coropceanu and J.-L. Brédas,ACS Appl. Mater. Interfaces, 2017,9, 18095–18102

    work page 2017

  33. [33]

    Tecmer, M

    P. Tecmer, M. Gałyńska, L. Szczuczko and K. Boguslawski,J. Phys. Chem. Lett., 2023,14, 9909–9917

    work page 2023

  34. [34]

    Jahani, K

    S. Jahani, K. Boguslawski and P. Tecmer,RSC Adv., 2023,13, 27898–27911

    work page 2023

  35. [35]

    Szczuczko, M

    L. Szczuczko, M. Gałyńska, M. H. Kriebel, P. Tecmer and K. Boguslawski,J. Chem. Theory Comput., 2025,21, 4506–4519

    work page 2025

  36. [36]

    M. B. Smith and J. Michl,Chem. Rev., 2010,110, 6891–6936

    work page 2010

  37. [37]

    M. E. Sandoval-Salinas and D. Casanova,ChemPhotoChem, 2021,5, 282–293

    work page 2021

  38. [38]

    de Silva,J

    P. de Silva,J. Phys. Chem. Lett., 2019,10, 5674–5679

    work page 2019

  39. [39]

    Aizawa, Y.-J

    N. Aizawa, Y.-J. Pu, Y. Harabuchi, A. Nihonyanagi, R. Ibuka, H. Inuzuka, B. Dhara, Y. Koyama, K. Nakayama, S. Maeda et al.,Nature, 2022,609, 502–506

    work page 2022

  40. [40]

    Boguslawski, A

    K. Boguslawski, A. Leszczyk, A. Nowak, F. Brzęk, P. S. Żuchowski, D. Kędziera and P. Tecmer,Comput. Phys. Commun., 2021,264, 107933

    work page 2021

  41. [41]

    Boguslawski, F

    K. Boguslawski, F. Brzęk, R. Chakraborty, K. Cieślak, S. Jahani, A. Leszczyk, A. Nowak, E. Sujkowski, J. Świerczyński, S. Ahmadkhani, D. Kędziera, M. H. Kriebel, P. S. Żuchowski and P. Tecmer,Comput. Phys. Commun., 2024,297, 109049

    work page 2024

  42. [42]

    Boguslawski and P

    K. Boguslawski and P. W. Ayers,J. Chem. Theory Comput., 2015,11, 5252–5261

    work page 2015

  43. [43]

    Boguslawski, P

    K. Boguslawski, P. Tecmer, P. W. Ayers, P. Bultinck, S. De Baerdemacker and D. Van Neck,Phys. Rev. B, 2014,89, 201106(R)

    work page 2014

  44. [44]

    Stein, T

    T. Stein, T. M. Henderson and G. E. Scuseria,J. Chem. Phys., 2014,140, 214113

    work page 2014

  45. [45]

    Tecmer, K

    P. Tecmer, K. Boguslawski, P. A. Limacher, P. A. Johnson, M. Chan, T. Verstraelen and P. W. Ayers,J. Phys. Chem. A, 2014,118, 9058–9068

    work page 2014

  46. [46]

    Boguslawski, P

    K. Boguslawski, P. Tecmer, P. A. Limacher, P. A. Johnson, P. W. Ayers, P. Bultinck, S. De Baerdemacker and D. Van Neck,J. Chem. Phys., 2014,140, 214114

    work page 2014

  47. [47]

    Tecmer, K

    P. Tecmer, K. Boguslawski and P. W. Ayers,Phys. Chem. Chem. Phys., 2015,17, 14427–14436

    work page 2015

  48. [48]

    Boguslawski, P

    K. Boguslawski, P. Tecmer and Ö. Legeza,Phys. Rev. B, 2016,94, 155126

    work page 2016

  49. [49]

    Boguslawski,J

    K. Boguslawski,J. Chem. Phys., 2016,145, 234105

    work page 2016

  50. [50]

    Boguslawski,J

    K. Boguslawski,J. Chem. Phys., 2017,147, 139901. 10

    work page 2017

  51. [51]

    Boguslawski,J

    K. Boguslawski,J. Chem. Theory Comput., 2019,15, 18–24

    work page 2019

  52. [52]

    S. J. Bintrim and K. Carter-Fenk,J. Chem. Theory Comput., 2025,21, 4080–4094

    work page 2025

  53. [53]

    Ahmadkhani, K

    S. Ahmadkhani, K. Boguslawski and P. Tecmer,J. Chem. Theory Comput., 2024,20, 10443–10452

    work page 2024

  54. [54]

    J. N. Byrd, V. Rishi, A. Perera and R. J. Bartlett,J. Chem. Phys., 2015,143, 164103

    work page 2015

  55. [55]

    Carter-Fenk,J

    K. Carter-Fenk,J. Phys. Chem. A, 2025,129, 7251–7260

    work page 2025

  56. [57]

    Chakraborty, K

    R. Chakraborty, K. Boguslawski and P. Tecmer,Phys. Chem. Chem. Phys., 2023,25, 25377–25388

    work page 2023

  57. [58]

    Boguslawski, P

    K. Boguslawski, P. Tecmer, P. W. Ayers, P. Bultinck, S. De Baerdemacker and D. Van Neck,J. Chem. Theory Comput., 2014,10, 4873–4882

    work page 2014

  58. [59]

    P. A. Limacher, P. W. Ayers, P. A. Johnson, S. De Baerdemacker, D. Van Neck and P. Bultinck,J. Chem. Theory Comput., 2013,9, 1394–1401

    work page 2013

  59. [60]

    Tecmer and K

    P. Tecmer and K. Boguslawski,Phys. Chem. Chem. Phys., 2022,24, 23026–23048

    work page 2022

  60. [61]

    P. A. Limacher, T. D. Kim, P. W. Ayers, P. A. Johnson, S. De Baerdemacker, D. Van Neck and P. Bultinck,Mol. Phys., 2014,112, 853–862

    work page 2014

  61. [62]

    Martínez González, D

    M. Martínez González, D. F. Calero-Osorio, M. Richer, C. Masschelein, S. Wang, P. A. Johnson, S. De Baerdemacker and P. W. Ayers,J. Chem. Phys., 2025,163, 144122

    work page 2025

  62. [63]

    Kossoski, A

    F. Kossoski, A. Marie, A. Scemama, M. Caffarel and P.-F. Loos,J. Chem. Theory Comput., 2021,17, 4756–4768

    work page 2021

  63. [64]

    Limacher, P

    P. Limacher, P. Ayers, P. Johnson, S. De Baerdemacker, D. Van Neck and P. Bultinck,Phys. Chem. Chem. Phys, 2014, 16, 5061–5065

    work page 2014

  64. [65]

    Boguslawski and P

    K. Boguslawski and P. Tecmer,J. Chem. Theory Comput., 2017,13, 5966–5983

    work page 2017

  65. [66]

    D. F. Calero-Osorio and P. W. Ayers,J. Chem. Phys., 2026,164, 104105

    work page 2026

  66. [67]

    T. M. Henderson, I. W. Bulik, T. Stein and G. E. Scuseria,J. Chem. Phys., 2014,141, 244104

    work page 2014

  67. [68]

    Leszczyk, M

    A. Leszczyk, M. Máté, Ö. Legeza and K. Boguslawski,J. Chem. Theory Comput., 2022,18, 96–117

    work page 2022

  68. [69]

    Oliphant and L

    N. Oliphant and L. Adamowicz,J. Chem. Phys., 1991,94, 1229–1235

    work page 1991

  69. [70]

    Oliphant and L

    N. Oliphant and L. Adamowicz,J. Chem. Phys., 1992,96, 3739–3744

    work page 1992

  70. [71]

    Piecuch, N

    P. Piecuch, N. Oliphant and L. Adamowicz,J. Chem. Phys., 1993,99, 1875–1900

    work page 1993

  71. [72]

    Piecuch and L

    P. Piecuch and L. Adamowicz,J. Chem. Phys., 1994,100, 5792–5809

    work page 1994

  72. [73]

    Sekino and R

    H. Sekino and R. J. Bartlett,Int. J. Quantum Chem., 1984,18, 255–265

    work page 1984

  73. [74]

    Koch and P

    H. Koch and P. Jørgensen,J. Chem. Phys., 1990,93, 3333–3344

    work page 1990

  74. [75]

    H. Koch, H. J. A. Jensen, P. Jørgensen and T. Helgaker,J. Chem. Phys., 1990,93, 3345–3350

    work page 1990

  75. [76]

    Christiansen, P

    O. Christiansen, P. Jørgensen and C. Hättig,Int. J. Quantum Chem., 1998,68, 1–52

    work page 1998

  76. [77]

    M. Ravi, A. Perera, Y. C. Park and R. J. Bartlett,J. Chem. Phys., 2023,159, 094101

    work page 2023

  77. [78]

    Nowak, P

    A. Nowak, P. Tecmer and K. Boguslawski,Phys. Chem. Chem. Phys., 2019,21, 19039–19053

    work page 2019

  78. [79]

    and Jørgensen, P

    Helgaker, T. and Jørgensen, P. and Olsen, J.,Molecular electronic-structure theory, Wiley, New York, 2000

    work page 2000

  79. [80]

    Szczuczko and K

    L. Szczuczko and K. Boguslawski,Int. J. Quantum Chem., 2025,125, e70095

    work page 2025

  80. [81]

    T. H. Dunning Jr,J. Chem. Phys., 1989,90, 1007–1023

    work page 1989

Showing first 80 references.