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dc.contributor.authorCapelle, K.eng
dc.contributor.authorVignale, Giovanni, 1957-eng
dc.contributor.authorUllrich, Carsten A.eng
dc.date.issued2010eng
dc.descriptionURL:http://link.aps.org/doi/10.1103/PhysRevB.81.125114 DOI:10.1103/PhysRevB.81.125114eng
dc.description.abstractEnergy gaps are crucial aspects of the electronic structure of finite and extended systems. Whereas much is known about how to define and calculate charge gaps in density-functional theory (DFT), and about the relation between these gaps and derivative discontinuities of the exchange-correlation functional, much less is known about spin gaps. In this paper we give density-functional definitions of spin-conserving gaps, spin-flip gaps and the spin stiffness in terms of many-body energies and in terms of single-particle (Kohn-Sham) energies. Our definitions are as analogous as possible to those commonly made in the charge case, but important differences between spin and charge gaps emerge already on the single-particle level because unlike the fundamental charge gap spin gaps involve excited-state energies. Kohn-Sham and many-body spin gaps are predicted to differ, and the difference is related to derivative discontinuities that are similar to, but distinct from, those usually considered in the case of charge gaps. Both ensemble DFT and time-dependent DFT (TDDFT) can be used to calculate these spin discontinuities from a suitable functional. We illustrate our findings by evaluating our definitions for the Lithium atom, for which we calculate spin gaps and spin discontinuities by making use of near-exact Kohn-Sham eigenvalues and, independently, from the single-pole approximation to TDDFT. The many-body corrections to the Kohn-Sham spin gaps are found to be negative, i.e., single-particle calculations tend to overestimate spin gaps while they underestimate charge gaps.eng
dc.description.sponsorshipK.C. thanks the Physics Department of the University of Missouri-Columbia, where part of this work was done, for generous hospitality, and D. Vieira for preparing and discussing Fig. 1. K.C. is supported by Brazilian funding agencies FAPESP and CNPq. C.A.U. acknowledges support from NSF Grant No. DMR-0553485. C.A.U. would also like to thank the KITP Santa Barbara for its hospitality and partial support under NSF Grant No. PHY05-51164. G.V. acknowledges support from NSF Grant No. DMR-0705460.eng
dc.identifier.citationPhys. Rev. B 81, 125114 (2010)eng
dc.identifier.issn1098-0121eng
dc.identifier.urihttp://hdl.handle.net/10355/7573eng
dc.languageEnglisheng
dc.publisherAmerican Physical Societyeng
dc.relation.ispartofcollectionUniversity of Missouri--Columbia. College of Arts and Sciences. Department of Physics and Astronomy. Physics and Astronomy publicationseng
dc.subjectspin gapseng
dc.subjectspin-flip gapseng
dc.subjectspin stiffnesseng
dc.subject.lcshEnergy gap (Physics)eng
dc.subject.lcshSpintronicseng
dc.titleSpin gaps and spin-flip energies in density-functional theoryeng
dc.typeArticleeng


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