This work deals with the variational determination of the two-particle reduced density matrix (2-RDM) and the energy corresponding to the ground state of N-particle systems within the doubly occupied configuration interaction (DOCI) space. Here, we impose for the first time up to four-particle N-representability constraint conditions in the variational determination of the 2-RDM matrix elements using the standard semidefinite programming algorithms. The energies and 2-RDMs obtained from this treatment and the corresponding computational costs are compared with those arisen from previously reported less restrictive variational methods [D. R. Alcoba et al., J. Chem. Phys. 149, 194105 (2018)] as well as with the exact DOCI values. We apply the different approximations to the one-dimensional XXZ model of quantum magnetism, which has a rich phase diagram with one critical phase and constitutes a stringent test for the method. The numerical results show the usefulness of our treatment to achieve a high degree of accuracy.
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21 October 2019
Research Article|
October 15 2019
Variational reduced density matrix method in the doubly-occupied configuration interaction space using four-particle N-representability conditions: Application to the XXZ model of quantum magnetism
A. Rubio-García
;
A. Rubio-García
1
Instituto de Estructura de la Materia, CSIC
, Serrano 123, 28006 Madrid, Spain
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J. Dukelsky
;
J. Dukelsky
1
Instituto de Estructura de la Materia, CSIC
, Serrano 123, 28006 Madrid, Spain
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D. R. Alcoba
;
D. R. Alcoba
a)
2
Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria
, 1428 Buenos Aires, Argentina
3
Instituto de Física de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria
, 1428 Buenos Aires, Argentina
a)Author to whom correspondence should be addressed: dalcoba@df.uba.ar
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P. Capuzzi
;
P. Capuzzi
2
Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria
, 1428 Buenos Aires, Argentina
3
Instituto de Física de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria
, 1428 Buenos Aires, Argentina
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O. B. Oña
;
O. B. Oña
4
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, CCT La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas
, Diag. 113 y 64 (S/N), Sucursal 4, CC 16, 1900 La Plata, Argentina
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E. Ríos
;
E. Ríos
4
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, CCT La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas
, Diag. 113 y 64 (S/N), Sucursal 4, CC 16, 1900 La Plata, Argentina
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A. Torre
;
A. Torre
5
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco
, Apdo. 644, E-48080 Bilbao, Spain
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L. Lain
L. Lain
5
Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco
, Apdo. 644, E-48080 Bilbao, Spain
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a)Author to whom correspondence should be addressed: dalcoba@df.uba.ar
J. Chem. Phys. 151, 154104 (2019)
Article history
Received:
July 06 2019
Accepted:
September 24 2019
Citation
A. Rubio-García, J. Dukelsky, D. R. Alcoba, P. Capuzzi, O. B. Oña, E. Ríos, A. Torre, L. Lain; Variational reduced density matrix method in the doubly-occupied configuration interaction space using four-particle N-representability conditions: Application to the XXZ model of quantum magnetism. J. Chem. Phys. 21 October 2019; 151 (15): 154104. https://doi.org/10.1063/1.5118899
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