Generalized spin in the variational determination of two-electron reduced density matrices within the doubly occupied configuration interaction framework
Abstract
This work extends the variational determination of two-electron reduced density matrices to the generalized spin formulation within the doubly occupied configuration interaction treatment. We describe electronic states of N-electron systems by means of variational evaluation of the corresponding two-electron reduced density matrix elements, subject to determined N-representability conditions, arising from the restricted, unrestricted, and generalized spin approaches. The results are compared with those predicted by the counterpart treatments involving wave functions. We report potential energy curves for a series of hydrogen atom clusters with different geometries in the presence of an external uniform magnetic field. These results allow us to analyze and discuss crossings between potential energy curves involving transitions between electronic states of different spin multiplicities. The predictions provided by these methods have been contrasted with the results arising from the full configuration interaction procedure, confirming changes of ⟨Ŝ2⟩ and ⟨Ŝz⟩ expectation values.
Article Details
Journal Info
The Journal of Chemical Physics
American Institute of Physics
Authors (7)
Tomás R. Ayala
Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Física, Ciudad Universitaria 1 , 1428 Buenos Aires,
Elías Ríos
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas 2 , Diag. 113 y 64 (S/N), Sucursal 4, CC 16, 1900 La Plata,
Ofelia B. Oña
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas 2 , Diag. 113 y 64 (S/N), Sucursal 4, CC 16, 1900 La Plata,
Luis Lain
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco 3 , Apdo. 644, E-48080 Bilbao,
Alicia Torre
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco 3 , Apdo. 644, E-48080 Bilbao,
Gustavo E. Massaccesi
Departamento de Ciencias Exactas, Ciclo Básico Común, Universidad de Buenos Aires, Ciudad Universitaria 4 , 1428 Buenos Aires,
Diego R. Alcoba
Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Física, Ciudad Universitaria 1 , 1428 Buenos Aires,