Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states
Abstract
Multireference quantum chemical methods, such as the complete active space selfconsistent field (CASSCF) method, have long been the state of the art for computing regions of potential energy surfaces (PESs) where complex, multiconfigurational wavefunctions are required, such as near conical intersections. Herein, we present a computationally efficient alternative to the widely used CASSCF method based on a complete active space configuration interaction (CASCI) expansion built from the stateaveraged natural orbitals of configuration interaction singles calculations (CISNOs). This CISNOCASCI approach is shown to predict vertical excitation energies of molecules with closedshell ground states similar to those predicted by state averaged (SA)CASSCF in many cases and to provide an excellent reference for a perturbative treatment of dynamic electron correlation. Absolute energies computed at the CISNOCASCI level are found to be variationally superior, on average, to other CASCI methods. Unlike SACASSCF, CISNOCASCI provides vertical excitation energies which are both size intensive and size consistent, thus suggesting that CISNOCASCI would be preferable to SACASSCF for the study of systems with multiple excitable centers. The fact that SACASSCF and some other CASCI methods do not provide a size intensive/consistent description of excited states is attributed to changes in the orbitals that occur upon introduction ofmore »
 Authors:
 Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (United States)
 Department of Chemistry, City College of New York, New York, New York 10031 (United States)
 Publication Date:
 OSTI Identifier:
 22415818
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CONFIGURATION INTERACTION; ELECTRON CORRELATION; ETHYLENE; EXCITATION; EXCITED STATES; GROUND STATES; MOLECULES; POTENTIAL ENERGY; SELFCONSISTENT FIELD; SURFACES; VARIATIONAL METHODS
Citation Formats
Shu, Yinan, Levine, Benjamin G., Email: levine@chemistry.msu.edu, and Hohenstein, Edward G. Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states. United States: N. p., 2015.
Web. doi:10.1063/1.4905124.
Shu, Yinan, Levine, Benjamin G., Email: levine@chemistry.msu.edu, & Hohenstein, Edward G. Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states. United States. doi:10.1063/1.4905124.
Shu, Yinan, Levine, Benjamin G., Email: levine@chemistry.msu.edu, and Hohenstein, Edward G. 2015.
"Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states". United States.
doi:10.1063/1.4905124.
@article{osti_22415818,
title = {Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states},
author = {Shu, Yinan and Levine, Benjamin G., Email: levine@chemistry.msu.edu and Hohenstein, Edward G.},
abstractNote = {Multireference quantum chemical methods, such as the complete active space selfconsistent field (CASSCF) method, have long been the state of the art for computing regions of potential energy surfaces (PESs) where complex, multiconfigurational wavefunctions are required, such as near conical intersections. Herein, we present a computationally efficient alternative to the widely used CASSCF method based on a complete active space configuration interaction (CASCI) expansion built from the stateaveraged natural orbitals of configuration interaction singles calculations (CISNOs). This CISNOCASCI approach is shown to predict vertical excitation energies of molecules with closedshell ground states similar to those predicted by state averaged (SA)CASSCF in many cases and to provide an excellent reference for a perturbative treatment of dynamic electron correlation. Absolute energies computed at the CISNOCASCI level are found to be variationally superior, on average, to other CASCI methods. Unlike SACASSCF, CISNOCASCI provides vertical excitation energies which are both size intensive and size consistent, thus suggesting that CISNOCASCI would be preferable to SACASSCF for the study of systems with multiple excitable centers. The fact that SACASSCF and some other CASCI methods do not provide a size intensive/consistent description of excited states is attributed to changes in the orbitals that occur upon introduction of noninteracting subsystems. Finally, CISNOCASCI is found to provide a suitable description of the PES surrounding a biradicaloid conical intersection in ethylene.},
doi = {10.1063/1.4905124},
journal = {Journal of Chemical Physics},
number = 2,
volume = 142,
place = {United States},
year = 2015,
month = 1
}

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