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Title: Half-metallicity and spin-contamination of the electronic ground state of graphene nanoribbons and related systems: An impossible compromise?
Authors: Huzak, Matija
Deleuze, Michael S.
Hajgato, Balazs
Issue Date: 2011
Citation: JOURNAL OF CHEMICAL PHYSICS, 135, p. 104704-104718
Abstract: An analysis using the formalism of crystalline orbitals for extended systems with periodicity in one dimension demonstrates that any antiferromagnetic and half-metallic spin-polarization of the edge states in n-acenes, and more generally in zigzag graphene anoislands and nanoribbons of finite width, would imply a spin contamination <S2> that increases proportionally to system size, in sharp and clear contradiction with the implications of Lieb’s theorem for compensated bipartite lattices and the expected value for a singlet (S = 0) electronic ground state. Verifications on naphthalene, larger n-acenes (n = 3–10) and rectangular nanographene islands of increasing size, as well as a comparison using unrestricted Hartree-Fock theory along with basis sets of improving quality against various many-body treatments demonstrate altogether that antiferromagnetism and half-metallicity in extended graphene nanoribbons will be quenched by an exact treatment of electron correlation, at the confines of non-relativistic many-body quantum mechanics. Indeed, for singlet states, symmetry breakings in spin-densities are necessarily the outcome of a too approximate treatment of static and dynamic electron correlation in single-determinantal approaches, such as unrestricted Hartree-Fock or Density Functional Theory. In this context, such as the size-extensive spin-contamination to which it relates, half-metallicity is thus nothing else than a methodological artefact.
Notes: Reprint Address: Deleuze, MS (reprint author), Hasselt Univ, Agoralaan,Gebouw D, B-3590 Diepenbeek, Belgium - Addresses: 1. Hasselt Univ, B-3590 Diepenbeek, Belgium - E-mail Address: michael.deleuze@uhasselt.be
URI: http://hdl.handle.net/1942/13102
DOI: 10.1063/1.3626554
ISI #: 000296032400049
ISSN: 0021-9606
Category: A1
Type: Journal Contribution
Validation: ecoom, 2012
Appears in Collections: Research publications

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