Eur. Phys. J. D 38, 507-514 (2006)
https://doi.org/10.1140/epjd/e2006-00038-x

Electron correlations in a C₂₀ fullerene cluster

A lattice density-functional study of the Hubbard model

¹ Instituto Potosino de Investigación Científica y Tecnológica, Camino a la presa San José 2055, 78216 San Luis Potosí, Mexico
² Laboratoire de Physique Quantique, Centre National de la Recherche Scientifique, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France
³ Laboratoire de Nanophysique Magnétisme et Optoélectronique, Institut National des Sciences Appliquées, 135 avenue de Rangueil, 31062 Toulouse, France

Corresponding author: ^a gustavo.pastor@irsamc.ups-tlse.fr

Received: 15 June 2005
Revised: 27 September 2005
Published online: 21 February 2006

Abstract

The ground-state properties of C₂₀ fullerene clusters are determined in the framework of the Hubbard model by using lattice density-functional theory (LDFT) and scaling approximations to the interaction-energy functional. Results are given for the ground-state energy, kinetic and Coulomb energies, local magnetic moments, and charge-excitation gap, as a function of the Coulomb repulsion U/t and for electron or hole doping δ close to half-band filling (|δ| ≤1). The role of electron correlations is analyzed by comparing the LDFT results with fully unrestricted Hartree-Fock (UHF) calculations which take into account possible noncollinear arrangements of the local spin-polarizations. The consequences of the spin-density-wave symmetry breaking, often found in UHF, and the implications of this study for more complex fullerene structures are discussed.