1. Spin contamination-free N -electron wave functions in the excitation-based configuration interaction treatment
- Author
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Pablo Capuzzi, Gustavo E. Massaccesi, Luis Lain, Alicia Torre, Diego Ricardo Alcoba, and Ofelia Beatriz Oña
- Subjects
Detección de Spin ,Ciencias Físicas ,General Physics and Astronomy ,Expectation value ,Electrones ,010402 general chemistry ,01 natural sciences ,Spin contamination ,purl.org/becyt/ford/1 [https] ,Operator (computer programming) ,Quantum mechanics ,0103 physical sciences ,Physical and Theoretical Chemistry ,Wave function ,Physics ,010304 chemical physics ,Física ,Multireference configuration interaction ,Química ,purl.org/becyt/ford/1.3 [https] ,Configuration interaction ,Eigenfunction ,0104 chemical sciences ,Astronomía ,Slater determinant ,Atomic physics ,CIENCIAS NATURALES Y EXACTAS - Abstract
This work deals with the spin contamination in N-electron wave functions provided by the excitation-based configuration interaction methods. We propose a procedure to ensure a suitable selection of excited N-electron Slater determinants with respect to a given reference determinant, required in these schemes. The procedure guarantees the construction of N-electron wave functions which are eigenfunctions of the spin-squared operator S 2, avoiding any spin contamination. Our treatment is based on the evaluation of the excitation level of the determinants by means of the expectation value of an excitation operator formulated in terms of spin-free replacement operators. We report numerical determinations of energies and S 2 expectation values, arising from our proposal as well as from traditional configuration interaction methods, in selected open-shell systems, in order to compare the behavior of these procedures and their computational costs., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
- Published
- 2016