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The electronic structures of BEDT-TTF·PF6 crystals; a comparison of self-consistent field and Hubbard model analyses


Ping Tang, N. A. W. Holzwarth, Freddie Salsbury, Jr. and Jeremy Qualls
submitted to Phys. Rev. B PDF

There has been considerable experimental and theoretical interest in synthetic materials formed from charge transfer salts of BEDT-TTF (bis-ethylenedithio-tetrathiafulvalene). Three crystalline formsof (BEDT-TTF)·PF6 have been identified experimentally, and labeled δ, ε, and ζ. We have modeled these three materials using first-principles self-consistent field methods, to determine the optimal geometrical parameters, the densities of state, and electron density contour plots for states near the Fermi level. The ε and ζ crystals are found to be metallic, while the δ crystals, with twice as many molecules per unit cell, are found to be insulating. By contrast, experimental conductivity and optical measurements for the ζ material suggest a Mott insulator behavior. We examine the Hubbard model for this system to understand both the Mott insulating behavior and the failure of the self-consistent field methods to model it.



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