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Extended Dynamically Weighted CASPT2: The Best of Two Worlds

[Image: see text] We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to e...

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Autores principales: Battaglia, Stefano, Lindh, Roland
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2020
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307887/
https://www.ncbi.nlm.nih.gov/pubmed/32027802
http://dx.doi.org/10.1021/acs.jctc.9b01129
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author Battaglia, Stefano
Lindh, Roland
author_facet Battaglia, Stefano
Lindh, Roland
author_sort Battaglia, Stefano
collection PubMed
description [Image: see text] We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order references are near-degenerate. Our approach follows a recipe analogous to that of XMS-CASPT2 to ensure approximate invariance under unitary transformations of the model states and a dynamic weighting scheme to smoothly interpolate the Fock operator between state-specific and state-average regimes. The resulting extended dynamically weighted CASPT2 (XDW-CASPT2) methodology possesses the most desirable features of both MS-CASPT2 and XMS-CASPT2, that is, the ability to provide accurate transition energies and correctly describe avoided crossings and conical intersections. The reliability of XDW-CASPT2 is assessed on a number of molecular systems. First, we consider the dissociation of lithium fluoride, highlighting the distinctive characteristics of the new approach. Second, the invariance of the theory is investigated by studying the conical intersection of the distorted allene molecule. Finally, the relative accuracy in the calculation of vertical excitation energies is benchmarked on a set of 26 organic compounds. We found that XDW-CASPT2, albeit being only approximately invariant, produces smooth potential energy surfaces around conical intersections and avoided crossings, performing equally well to the strictly invariant XMS-CASPT2 method. The accuracy of vertical transition energies is almost identical to MS-CASPT2, with a mean absolute deviation of 0.01–0.02 eV, in contrast to 0.12 eV for XMS-CASPT2.
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spelling pubmed-73078872020-06-23 Extended Dynamically Weighted CASPT2: The Best of Two Worlds Battaglia, Stefano Lindh, Roland J Chem Theory Comput [Image: see text] We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order references are near-degenerate. Our approach follows a recipe analogous to that of XMS-CASPT2 to ensure approximate invariance under unitary transformations of the model states and a dynamic weighting scheme to smoothly interpolate the Fock operator between state-specific and state-average regimes. The resulting extended dynamically weighted CASPT2 (XDW-CASPT2) methodology possesses the most desirable features of both MS-CASPT2 and XMS-CASPT2, that is, the ability to provide accurate transition energies and correctly describe avoided crossings and conical intersections. The reliability of XDW-CASPT2 is assessed on a number of molecular systems. First, we consider the dissociation of lithium fluoride, highlighting the distinctive characteristics of the new approach. Second, the invariance of the theory is investigated by studying the conical intersection of the distorted allene molecule. Finally, the relative accuracy in the calculation of vertical excitation energies is benchmarked on a set of 26 organic compounds. We found that XDW-CASPT2, albeit being only approximately invariant, produces smooth potential energy surfaces around conical intersections and avoided crossings, performing equally well to the strictly invariant XMS-CASPT2 method. The accuracy of vertical transition energies is almost identical to MS-CASPT2, with a mean absolute deviation of 0.01–0.02 eV, in contrast to 0.12 eV for XMS-CASPT2. American Chemical Society 2020-02-06 2020-03-10 /pmc/articles/PMC7307887/ /pubmed/32027802 http://dx.doi.org/10.1021/acs.jctc.9b01129 Text en Copyright © 2020 American Chemical Society This is an open access article published under a Creative Commons Attribution (CC-BY) License (http://pubs.acs.org/page/policy/authorchoice_ccby_termsofuse.html) , which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
spellingShingle Battaglia, Stefano
Lindh, Roland
Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title_full Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title_fullStr Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title_full_unstemmed Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title_short Extended Dynamically Weighted CASPT2: The Best of Two Worlds
title_sort extended dynamically weighted caspt2: the best of two worlds
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307887/
https://www.ncbi.nlm.nih.gov/pubmed/32027802
http://dx.doi.org/10.1021/acs.jctc.9b01129
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