Toward the parametrization of the Hubbard model for salts of bis(ethylenedithio)tetrathiafulvalene: A density functional study of isolated molecules

Scriven, Edan and Powell, B. J. (2009) Toward the parametrization of the Hubbard model for salts of bis(ethylenedithio)tetrathiafulvalene: A density functional study of isolated molecules. Journal of Chemical Physics, 130 10: 104508.1-104508.10. doi:10.1063/1.3080543

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Author Scriven, Edan
Powell, B. J.
Title Toward the parametrization of the Hubbard model for salts of bis(ethylenedithio)tetrathiafulvalene: A density functional study of isolated molecules
Journal name Journal of Chemical Physics   Check publisher's open access policy
ISSN 0021-9606
1089-7690
Publication date 2009-03-13
Year available 2009
Sub-type Article (original research)
DOI 10.1063/1.3080543
Open Access Status File (Publisher version)
Volume 130
Issue 10
Start page 104508.1
End page 104508.10
Total pages 10
Editor Donald Levy
Place of publication College Park, MD, United States
Publisher American Institute of Physics
Collection year 2010
Language eng
Subject C1
0204 Condensed Matter Physics
970102 Expanding Knowledge in the Physical Sciences
Abstract We calculate the effective Coulomb repulsion between electrons/holes Um(v) and site energy for an isolated bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) molecule in vacuo. Um(v) = 4.2±0.1 eV for 44 experimental geometries taken from a broad range of conformations, polymorphs, anions, temperatures, and pressures (the quoted “error” is one standard deviation). Hence we conclude that Um(v) is essentially the same for all of the compounds studied. This shows that the strong (hydrostatic and chemical) pressure dependence observed in the phase diagrams of the BEDT-TTF salts is not due to Um(v). Therefore, if the Hubbard model is sufficient to describe the phase diagram of the BEDT-TTF salts, there must be significant pressure dependence on the intramolecular terms in the Hamiltonian and/or the reduction in the Hubbard U due to the interaction of the molecule with the polarizable crystal environment. The renormalized value of Um(v) is significantly smaller than the bare value of the Coulomb integral, F0 = 5.2±0.1 eV, across the same set of geometries, emphasizing the importance of using the renormalized value of Um(v). The site energy (for holes), ξm = 5.0±0.2 eV, varies only a little more than Um(v) across the same set of geometries. However, we argue that this variation in the site energy plays a key role in understanding the role of disorder in bis(ethylenedithio)tetrathiafulvalene salts. We explain the differences between the βL and βH phases of (BEDT-TTF)2I3 on the basis of calculations of the effects of disorder.
Keyword Density functional theory
Shell Hamiltonian method
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Thu, 03 Sep 2009, 08:29:12 EST by Mr Andrew Martlew on behalf of School of Mathematics & Physics