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Tuckman H, Neuscamman E. Aufbau Suppressed Coupled Cluster Theory for Electronically Excited States. J Chem Theory Comput 2024; 20:2761-2773. [PMID: 38502102 DOI: 10.1021/acs.jctc.3c01285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
We introduce an approach to improve single-reference coupled cluster theory in settings where the Aufbau determinant is absent from or plays only a small role in the true wave function. Using a de-excitation operator that can be efficiently hidden within a similarity transform, we create a coupled cluster wave function in which de-excitations work to suppress the Aufbau determinant and produce wave functions dominated by other determinants. Thanks to an invertible and fully exponential form, the approach is systematically improvable, size consistent, size extensive, and, interestingly, size intensive in a granular way that should make the adoption of some ground state techniques, such as local correlation, relatively straightforward. In this initial study, we apply the general formalism to create a state-specific method for orbital-relaxed, singly excited states. We find that this approach matches the accuracy of similar-cost equation-of-motion methods in valence excitations while offering improved accuracy for charge transfer states. We also find the approach to be more accurate than excited-state-specific perturbation theory in both types of states.
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Affiliation(s)
- Harrison Tuckman
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Eric Neuscamman
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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2
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Tuckman H, Neuscamman E. Excited-State-Specific Pseudoprojected Coupled-Cluster Theory. J Chem Theory Comput 2023; 19:6160-6171. [PMID: 37676752 DOI: 10.1021/acs.jctc.3c00194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
We present an excited-state-specific coupled-cluster approach in which both the molecular orbitals and cluster amplitudes are optimized for an individual excited state. The theory is formulated via a pseudoprojection of the traditional coupled-cluster wavefunction that allows correlation effects to be introduced atop an excited-state mean field starting point. The approach shares much in common with ground-state CCSD, including size extensivity and an N6 cost scaling. Preliminary numerical tests show that, when augmented with N5 cost perturbative corrections for key terms, the method can improve over excited-state-specific second-order perturbation theory in valence, charge transfer, and Rydberg states.
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Affiliation(s)
- Harrison Tuckman
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Eric Neuscamman
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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3
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Aoto YA. Geometric interpretation for coupled-cluster theory. A comparison of accuracy with the corresponding configuration interaction model. J Chem Phys 2022; 157:084109. [DOI: 10.1063/5.0099102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although coupled-cluster theory is well-known for its accuracy, the geometry associated to the manifold of wave functions reached by the coupled-cluster ansatz has not been deeply explored. In this article we look for an interpretation for the high accuracy of coupled-cluster theory based on how the manifold of coupled-cluster wave functions is embedded within the space of n-electron wave functions. We define the coupled-cluster and configuration interaction manifolds and measure the distances from the full configuration interaction (FCI) wave function to these manifolds. We clearly observe that the FCI wave function is closer to the coupled-cluster manifold, that is curved, than to the configuration interaction manifold, that is flat, for the selected systems studied in this work. Furthermore, the decomposition of the distances among these manifolds and wave functions into excitation ranks gives insights on the failure of the coupled-cluster approach for multireference systems. The present results show a new interpretation for the quality of the coupled-cluster method, as contrasted to the truncated configuration interaction approach, besides the well-established argument based on size-extensivity. Furthermore, we show how a geometric description of wave function methods can be used in electronic structure theory.
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Lischka H, Nachtigallová D, Aquino AJA, Szalay PG, Plasser F, Machado FBC, Barbatti M. Multireference Approaches for Excited States of Molecules. Chem Rev 2018; 118:7293-7361. [DOI: 10.1021/acs.chemrev.8b00244] [Citation(s) in RCA: 197] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Hans Lischka
- School of Pharmaceutical Sciences and Technology, Tianjin University, Tianjin 300072, P.R. China
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria
| | - Dana Nachtigallová
- Institute of Organic Chemistry and Biochemistry v.v.i., The Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, 78371 Olomouc, Czech Republic
| | - Adélia J. A. Aquino
- School of Pharmaceutical Sciences and Technology, Tianjin University, Tianjin 300072, P.R. China
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
- Institute for Soil Research, University of Natural Resources and Life Sciences Vienna, Peter-Jordan-Strasse 82, A-1190 Vienna, Austria
| | - Péter G. Szalay
- ELTE Eötvös Loránd University, Laboratory of Theoretical Chemistry, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
| | - Felix Plasser
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria
- Department of Chemistry, Loughborough University, Leicestershire LE11 3TU, United Kingdom
| | - Francisco B. C. Machado
- Departamento de Química, Instituto Tecnológico de Aeronáutica, São José dos Campos 12228-900, São Paulo, Brazil
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Brabec J, Banik S, Kowalski K, Pittner J. Perturbative universal state-selective correction for state-specific multi-reference coupled cluster methods. J Chem Phys 2016; 145:164106. [PMID: 27802607 DOI: 10.1063/1.4965826] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, we report an extension of our previous development of the universal state-selective (USS) multireference coupled-cluster (MRCC) formalism. It was shown [Brabec et al., J. Chem. Phys. 136, 124102 (2012)] and [Banik et al., J. Chem. Phys. 142, 114106 (2015)] that the USS(2) approach significantly improves the accuracy of Brillouin-Wigner and Mukherjee MRCC formulations, however, the numerical and storage costs associated with calculating highly excited intermediates pose a significant challenge, which can restrict the applicability of the USS(2) method. Therefore, we introduce a perturbative variant of the USS(2) approach (USS(pt)), which substantially reduces numerical overhead of the full USS(2) correction while preserving its accuracy. Since the new USS(pt) implementation calculates the triple and quadruple projections in on-the-fly manner, the memory bottleneck associated with the need of storing expensive recursive intermediates is entirely eliminated. On the example of several benchmark systems, we demonstrate accuracies of USS(pt) and USS(2) approaches and their efficiency in describing quasidegenerate electronic states. It is also shown that the USS(pt) method significantly alleviates problems associated with the lack of invariance of MRCC theories upon the rotation of active orbitals.
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Affiliation(s)
- Jiri Brabec
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
| | - Subrata Banik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
| | - Karol Kowalski
- William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA
| | - Jiří Pittner
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
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Ghosh A, Chaudhuri RK, Chattopadhyay S. Relativistic state-specific multireference coupled cluster theory description for bond-breaking energy surfaces. J Chem Phys 2016; 145:124303. [DOI: 10.1063/1.4962911] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ellis BH, Aggarwal S, Chakraborty A. Development of the Multicomponent Coupled-Cluster Theory for Investigation of Multiexcitonic Interactions. J Chem Theory Comput 2015; 12:188-200. [DOI: 10.1021/acs.jctc.5b00879] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Benjamin H. Ellis
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | - Somil Aggarwal
- Jamesville-DeWitt
High School, DeWitt, New York 13214, United States
| | - Arindam Chakraborty
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
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8
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Demel O, Pittner J, Neese F. A Local Pair Natural Orbital-Based Multireference Mukherjee’s Coupled Cluster Method. J Chem Theory Comput 2015; 11:3104-14. [DOI: 10.1021/acs.jctc.5b00334] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ondřej Demel
- J.
Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, 18223 Prague 8, Czech Republic
| | - Jiří Pittner
- J.
Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, 18223 Prague 8, Czech Republic
| | - Frank Neese
- Max Planck Institute
of Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
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Banik S, Ravichandran L, Brabec J, Hubač I, Kowalski K, Pittner J. Iterative universal state selective correction for the Brillouin-Wigner multireference coupled-cluster theory. J Chem Phys 2015; 142:114106. [PMID: 25796230 DOI: 10.1063/1.4914311] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
As a further development of the previously introduced a posteriori Universal State-Selective (USS) corrections [K. Kowalski, J. Chem. Phys. 134, 194107 (2011); J. Brabec et al., ibid. 136, 124102 (2012)], we suggest an iterative form of the USS correction by means of correcting effective Hamiltonian matrix elements. We also formulate USS corrections via the left Bloch equations. The convergence of the USS corrections with excitation level towards the full configuration interaction (FCI) limit is also investigated. Various forms of the USS and simplified diagonal USS corrections at the singles and doubles and perturbative triple levels are numerically assessed on several model systems and on the ozone and tetramethyleneethane molecules. It is shown that the iterative USS correction can successfully replace the previously developed a posteriori Brillouin-Wigner coupled cluster size-extensivity correction, while it is not sensitive to intruder states and performs well also in other cases when the a posteriori one fails, like, e.g., for the asymmetric vibration mode of ozone.
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Affiliation(s)
- Subrata Banik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
| | - Lalitha Ravichandran
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
| | - Jiří Brabec
- Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Ivan Hubač
- Department of Chemical Physics, Faculty of Mathematics and Physics, Comenius University, 84215 Bratislava, Slovakia
| | - Karol Kowalski
- William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA
| | - Jiří Pittner
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague 8, Czech Republic
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10
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Chattopadhyay S, Chaudhuri RK, Mahapatra US. State-specific multireference perturbation theory with improved virtual orbitals: Taming the ground state of F2, Be2,and N2. J Comput Chem 2015; 36:907-25. [DOI: 10.1002/jcc.23873] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 01/09/2015] [Accepted: 01/11/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Sudip Chattopadhyay
- Department of Chemistry; Indian Institute of Engineering Science and Technology; Shibpur Howrah 711103 India
| | | | - Uttam Sinha Mahapatra
- Department of Physics; Maulana Azad College; 8 Rafi Ahmed Kidwai Road Kolkata 700013 India
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11
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Chattopadhyay S, Mahapatra US, Chaudhuri RK. Dissociation of homonuclear diatomic halogens via multireference coupled cluster calculations. Mol Phys 2014. [DOI: 10.1080/00268976.2014.906675] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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Lyakh DI, Bartlett RJ. Algebraic connectivity analysis in molecular electronic structure theory II: total exponential formulation of second-quantised correlated methods. Mol Phys 2013. [DOI: 10.1080/00268976.2013.807946] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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13
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Bhaskaran-Nair K, Kowalski K. Bridging single and multireference coupled cluster theories with universal state selective formalism. J Chem Phys 2013; 138:204114. [DOI: 10.1063/1.4806768] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Parametric two-electron reduced-density-matrix method with application to diradical rectangular H4. COMPUT THEOR CHEM 2013. [DOI: 10.1016/j.comptc.2012.09.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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16
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Köhn A, Hanauer M, Mück LA, Jagau TC, Gauss J. State-specific multireference coupled-cluster theory. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2012. [DOI: 10.1002/wcms.1120] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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Bhaskaran-Nair K, Brabec J, Aprà E, van Dam HJJ, Pittner J, Kowalski K. Implementation of the multireference Brillouin-Wigner and Mukherjee's coupled cluster methods with non-iterative triple excitations utilizing reference-level parallelism. J Chem Phys 2012; 137:094112. [DOI: 10.1063/1.4747698] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Jagau TC, Gauss J. Linear-response theory for Mukherjee's multireference coupled-cluster method: Excitation energies. J Chem Phys 2012; 137:044116. [DOI: 10.1063/1.4734309] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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19
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Jagau TC, Gauss J. Linear-response theory for Mukherjee's multireference coupled-cluster method: Static and dynamic polarizabilities. J Chem Phys 2012; 137:044115. [DOI: 10.1063/1.4734308] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Brabec J, Bhaskaran-Nair K, Kowalski K, Pittner J, van Dam HJ. Towards large-scale calculations with State-Specific Multireference Coupled Cluster methods: Studies on dodecane, naphthynes, and polycarbenes. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.05.064] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Jagau TC, Gauss J. Ground and excited state geometries via Mukherjee’s multireference coupled-cluster method. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2011.10.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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22
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Mahapatra US, Chattopadhyay S. Diagnosis of the performance of the state-specific multireference coupled-cluster method with different truncation schemes. J Comput Chem 2012; 33:1285-303. [PMID: 22419455 DOI: 10.1002/jcc.22960] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 02/06/2012] [Accepted: 02/07/2012] [Indexed: 11/06/2022]
Abstract
We have tested the linked version of a iterative (partial) triples correction for the Jeziorski-Monkhorst ansatz based state-specific multireference coupled cluster (SS-MRCC) approach with singles and doubles (SD) excitations [abbreviated as SS-MRCCSDT-1a and SS-MRCCSDT-1a+d]. The assessments of SS-MRCCSDT-1a and SS-MRCCSDT-1a+d schemes have been performed on the ground potential energy surface (PES) of P4, Li(2),Be(2) systems which demand the MR description, and on study of the excitation energy between the ground and first excited state for P4 system. Illustrations in the isomerization of cyclobutadiene also show the power of the schemes. One of the designed features of the SS-MRCCSDT-n methods introduced here is that they do not require storage of the triples amplitudes. In the entire range of geometries, we found a definite improvement provided by SS-MRCC with SDT-1a and SDT-1a+d schemes over the standard SD one. In the nondegenerate regions of PES, the closeness of the performance of the single-reference CC to the SS-MRCC methods increases after inclusion of even partial triple excitations. Generally, the performance of the SS-MRCCSDT-1a+d approach is closer to the corresponding full configuration interaction (FCI) one than to the SS-MRCCSDT-1a specially in the degenerate geometries (as is evident from nonparallelism error). The deviation from FCI for the first excited state of the P4 model using various SS-MRCC theories with different truncation schemes obtained by converging on the second root of the effective Hamiltonian has also been reported. We also compare our results with the current generation state-of-the-art single and multireference CC calculations to envisage the usefulness of the present approach. Initial implementation indicates that the SS-MRCCSDT-n formalism can provide not only reliable excitation energies and barrier height even when used in a relatively small model space, but also offers a considerable promise in generating the entire energy surface with low nonparallelity error.
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Affiliation(s)
- Uttam Sinha Mahapatra
- Department of Physics, Maulana Azad College, 8 Rafi Ahmed KidwaiRoad, Kolkata 700013, India.
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23
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Hanauer M, Köhn A. Perturbative treatment of triple excitations in internally contracted multireference coupled cluster theory. J Chem Phys 2012; 136:204107. [DOI: 10.1063/1.4718700] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Brabec J, van Dam HJJ, Pittner J, Kowalski K. Universal state-selective corrections to multi-reference coupled-cluster theories with single and double excitations. J Chem Phys 2012; 136:124102. [DOI: 10.1063/1.3692969] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Brabec J, Pittner J, van Dam HJJ, Aprà E, Kowalski K. Parallel Implementation of Multireference Coupled-Cluster Theories Based on the Reference-Level Parallelism. J Chem Theory Comput 2012; 8:487-97. [DOI: 10.1021/ct200809m] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jiří Brabec
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic,
CZ-18223 Prague 8, Czech Republic
| | - Jiří Pittner
- J. Heyrovský Institute
of Physical Chemistry, Academy of Sciences of the Czech Republic,
CZ-18223 Prague 8, Czech Republic
| | - Hubertus J. J. van Dam
- William R. Wiley Environmental
Molecular Science Laboratory, Battelle, Pacific Northwest National
Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, United
States
| | - Edoardo Aprà
- William R. Wiley Environmental
Molecular Science Laboratory, Battelle, Pacific Northwest National
Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, United
States
| | - Karol Kowalski
- William R. Wiley Environmental
Molecular Science Laboratory, Battelle, Pacific Northwest National
Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, United
States
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Lyakh DI, Musiał M, Lotrich VF, Bartlett RJ. Multireference Nature of Chemistry: The Coupled-Cluster View. Chem Rev 2011; 112:182-243. [DOI: 10.1021/cr2001417] [Citation(s) in RCA: 363] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dmitry I. Lyakh
- Quantum Theory Project, University of Florida, Gainesville, Florida 32611, United States
| | - Monika Musiał
- Quantum Theory Project, University of Florida, Gainesville, Florida 32611, United States
| | - Victor F. Lotrich
- Quantum Theory Project, University of Florida, Gainesville, Florida 32611, United States
| | - Rodney J. Bartlett
- Quantum Theory Project, University of Florida, Gainesville, Florida 32611, United States
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Kowalski K. A universal state-selective approach to multireference coupled-cluster non-iterative corrections. J Chem Phys 2011; 134:194107. [DOI: 10.1063/1.3589896] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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28
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Bhaskaran-Nair K, Demel O, Šmydke J, Pittner J. Multireference state-specific Mukherjee's coupled cluster method with noniterative triexcitations using uncoupled approximation. J Chem Phys 2011; 134:154106. [DOI: 10.1063/1.3573373] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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29
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Mahapatra US, Chattopadhyay S. Evaluation of the performance of single root multireference coupled cluster method for ground and excited states, and its application to geometry optimization. J Chem Phys 2011; 134:044113. [DOI: 10.1063/1.3523573] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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