Generalized single excitation configuration interaction: an investigation into the impact of the inclusion of non-orthogonality on the calculation of core-excited states
Abstract
In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method for the calculation of core-excited states. Fully non-orthogonal CIS (NOCIS) has been described previously for species with singlet and doublet ground states, and this paper reports the extension to molecules in their triplet ground state. In addition to NOCIS, we present a novel method, one-center NOCIS (1C-NOCIS), for open-shell molecules which is intermediate between NOCIS and the computationally less demanding static exchange approximation (STEX). We explore this hierarchy of spin-pure methods for core excitations of molecules with singlet, doublet, and triplet ground states. We conclude that, while NOCIS provides the best results and preserves the spatial symmetry of the wavefunction, 1C-NOCIS retains much of the accuracy of NOCIS at a dramatically reduced cost. For molecules with closed-shell ground states, STEX and 1C-NOCIS are identical.
Additional Information
© 2020 the Owner Societies. Received 5th December 2019, Accepted 29th March 2020, First published on 31st March 2020. KJO thanks the members of the Head-Gordon group for fruitful discussions and Mickaël Delcey for the use of his spectrum plotting software. This work is supported by the Director, Office of Science, Office of Basic Energy Sciences of the US Department of Energy under contract No. DE-AC02-05CH11231. There are no conflicts to declare.Attached Files
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Additional details
- Eprint ID
- 102361
- Resolver ID
- CaltechAUTHORS:20200406-144453694
- DE-AC02-05CH11231
- Department of Energy (DOE)
- Created
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2020-04-06Created from EPrint's datestamp field
- Updated
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2023-06-01Created from EPrint's last_modified field