Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework

In this work we project the Hamiltonian of an N-electron system onto a set of N-electron determinants cataloged by their seniority numbers and their excitation levels with respect to a reference determinant. We show that, in open-shell systems, the diagonalization of the N-electron Hamiltonian matri...

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Autores principales:	Oña, Ofelia Beatriz, Massaccesi, Gustavo Ernesto, Capuzzi, Pablo
Publicado:	2018
Materias:	Configuration interaction methodology Excitation level operators Excitation levels in N-electron determinants Hybrid methods in CI treatments Seniority number of N-electron determinants Seniority number operators Spin contamination of wave functions
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00653276_v76_n_p315_Alcoba http://hdl.handle.net/20.500.12110/paper_00653276_v76_n_p315_Alcoba
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_00653276_v76_n_p315_Alcoba
record_format	dspace
spelling	paper:paper_00653276_v76_n_p315_Alcoba2023-06-08T15:06:04Z Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework Oña, Ofelia Beatriz Massaccesi, Gustavo Ernesto Capuzzi, Pablo Configuration interaction methodology Excitation level operators Excitation levels in N-electron determinants Hybrid methods in CI treatments Seniority number of N-electron determinants Seniority number operators Spin contamination of wave functions In this work we project the Hamiltonian of an N-electron system onto a set of N-electron determinants cataloged by their seniority numbers and their excitation levels with respect to a reference determinant. We show that, in open-shell systems, the diagonalization of the N-electron Hamiltonian matrix leads to eigenstates of the operator Ŝ2 when the excitation levels are counted in terms of spatial orbitals instead of spin-orbitals. Our proposal is based on the commutation relations between the N-electron operators seniority number and spatial excitation level, as well as between these operators and the spin operators Ŝ2 and Ŝz. Energy and 〈Ŝ2〉 expectation values of molecular systems obtained from our procedure are compared with those arising from the standard hybrid configuration interaction methods based on seniority numbers and spin-orbital-excitation levels. We analyze the behavior of these methods, evaluating their computational costs and establishing their usefulness. © 2018 Elsevier Inc. Fil:Oña, O.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Massaccesi, G.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Capuzzi, P. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2018 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00653276_v76_n_p315_Alcoba http://hdl.handle.net/20.500.12110/paper_00653276_v76_n_p315_Alcoba
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Configuration interaction methodology Excitation level operators Excitation levels in N-electron determinants Hybrid methods in CI treatments Seniority number of N-electron determinants Seniority number operators Spin contamination of wave functions
spellingShingle	Configuration interaction methodology Excitation level operators Excitation levels in N-electron determinants Hybrid methods in CI treatments Seniority number of N-electron determinants Seniority number operators Spin contamination of wave functions Oña, Ofelia Beatriz Massaccesi, Gustavo Ernesto Capuzzi, Pablo Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
topic_facet	Configuration interaction methodology Excitation level operators Excitation levels in N-electron determinants Hybrid methods in CI treatments Seniority number of N-electron determinants Seniority number operators Spin contamination of wave functions
description	In this work we project the Hamiltonian of an N-electron system onto a set of N-electron determinants cataloged by their seniority numbers and their excitation levels with respect to a reference determinant. We show that, in open-shell systems, the diagonalization of the N-electron Hamiltonian matrix leads to eigenstates of the operator Ŝ2 when the excitation levels are counted in terms of spatial orbitals instead of spin-orbitals. Our proposal is based on the commutation relations between the N-electron operators seniority number and spatial excitation level, as well as between these operators and the spin operators Ŝ2 and Ŝz. Energy and 〈Ŝ2〉 expectation values of molecular systems obtained from our procedure are compared with those arising from the standard hybrid configuration interaction methods based on seniority numbers and spin-orbital-excitation levels. We analyze the behavior of these methods, evaluating their computational costs and establishing their usefulness. © 2018 Elsevier Inc.
author	Oña, Ofelia Beatriz Massaccesi, Gustavo Ernesto Capuzzi, Pablo
author_facet	Oña, Ofelia Beatriz Massaccesi, Gustavo Ernesto Capuzzi, Pablo
author_sort	Oña, Ofelia Beatriz
title	Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
title_short	Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
title_full	Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
title_fullStr	Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
title_full_unstemmed	Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework
title_sort	hybrid treatments based on determinant seniority numbers and spatial excitation levels in the configuration interaction framework
publishDate	2018
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00653276_v76_n_p315_Alcoba http://hdl.handle.net/20.500.12110/paper_00653276_v76_n_p315_Alcoba
work_keys_str_mv	AT onaofeliabeatriz hybridtreatmentsbasedondeterminantsenioritynumbersandspatialexcitationlevelsintheconfigurationinteractionframework AT massaccesigustavoernesto hybridtreatmentsbasedondeterminantsenioritynumbersandspatialexcitationlevelsintheconfigurationinteractionframework AT capuzzipablo hybridtreatmentsbasedondeterminantsenioritynumbersandspatialexcitationlevelsintheconfigurationinteractionframework
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Hybrid Treatments Based on Determinant Seniority Numbers and Spatial Excitation Levels in the Configuration Interaction Framework

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