Characterization of the unoccupied and partially occupied states of TTF-TCNQ by XANES and first-principles calculations

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© 2003 American Physical Society (APS). This is the accepted version of the following article: Fraxedas, J. & Lee, Y. J. & Jiménez, I. & Gago, R. & Nieminen, Risto M. & Ordejón, P. & Canadell, E. 2003. Characterization of the unoccupied and partially occupied states of TTF-TCNQ by XANES and first-principles calculations. Physical Review B. Volume 68, Issue 19. 195115-1-11. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.68.195115, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.68.195115.
Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2003
Major/Subject
Mcode
Degree programme
Language
en
Pages
195115-1-11
Series
Physical Review B, Volume 68, Issue 19
Abstract
We report a combined experimental and theoretical study of the unoccupied electronic states of the neutral molecular organic materials TTF (tetrathiafulvalene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane) and of the one-dimensional metallic charge transfer salt TTF-TCNQ. The experimental density of states (DOS) is obtained by x-ray absorption near edge spectroscopy (XANES) with synchrotron light and the predicted DOS by means of first-principles density functional theory calculations. Most of the experimentally derived element-specific XANES features can be associated to molecular orbitals of defined symmetry. Because of the planar geometry of the TTF and TCNQ molecules and the polarization of the synchrotron light, the energy dependent σ or π character of the orbitals can be inferred from angular dependent XANES measurements. The present work represents the state of the art analysis of the XANES spectra of this type of materials and points out the need for additional work in order to elucidate the governing selection rules in the excitation process.
Description
Keywords
organic conductors, XANES, DFT
Other note
Citation
Fraxedas, J. & Lee, Y. J. & Jiménez, I. & Gago, R. & Nieminen, Risto M. & Ordejón, P. & Canadell, E. 2003. Characterization of the unoccupied and partially occupied states of TTF-TCNQ by XANES and first-principles calculations. Physical Review B. Volume 68, Issue 19. 195115-1-11. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.68.195115.