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  Excited States of Large Open-Shell Molecules: An Efficient, General, and Spin-Adapted Approach Based on a Restricted Open-Shell Ground State Wave function

Roemelt, M., & Neese, F. (2013). Excited States of Large Open-Shell Molecules: An Efficient, General, and Spin-Adapted Approach Based on a Restricted Open-Shell Ground State Wave function. The Journal of Physical Chemistry A, 117(14), 3069-3083. doi:10.1021/jp3126126.

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 Creators:
Roemelt, Michael1, Author              
Neese, Frank1, Author              
Affiliations:
1Research Department Neese, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023886              

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 Abstract: A spin-adapted configuration interaction with singles method that is based on a restricted open-shell reference function (ROCIS) with general total spin S is presented. All excited configuration state functions (CSFs) are generated with the aid of a spin-free second quantization formalism that only leads to CSFs within the first order interacting space. By virtue of the CSF construction, the formalism involves higher than singly excited determinants but not higher than singly excited configurations. Matrix elements between CSFs are evaluated on the basis of commutator relationships using a symbolic algebra program. The final equations were, however, hand-coded in order to maximize performance. The method can be applied to fairly large systems with more than 100 atoms in reasonable wall-clock times and also parallelizes well. Test calculations demonstrate that the approach is far superior to UHF-based configuration interaction with single excitations but necessarily falls somewhat short of quantitative accuracy due to the lack of dynamic correlation contributions. In order to implicitly account for dynamic correlation in a crude way, the program optionally allows for the use of Kohn–Sham orbitals in combination with a modest downscaling of two-electron integrals (DFT/ROCIS). All two-electron integrals of Kohn–Sham orbitals that appear in the Hamiltonian matrix are reduced by a total of three scaling parameters that are suitable for a wide range of molecules. Test calculations on open-shell organic radicals as well as transition metal complexes demonstrate the wide applicability of the method and its ability to calculate the electronic spectra of large molecular systems.

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Language(s): eng - English
 Dates: 2012-12-212013-04-022013-04-11
 Publication Status: Published in print
 Pages: 15
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/jp3126126
 Degree: -

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Title: The Journal of Physical Chemistry A
  Abbreviation : J. Phys. Chem. A
Source Genre: Journal
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Publ. Info: Columbus, OH : American Chemical Society
Pages: - Volume / Issue: 117 (14) Sequence Number: - Start / End Page: 3069 - 3083 Identifier: ISSN: 1089-5639
CoNE: https://pure.mpg.de/cone/journals/resource/954926947766_4