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Title: Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF

Abstract

The highest T{sub c} organic superconductors all involve the organic molecule bis(ethylenedithio)tetrathiafulvalene (denoted as BEDT-TTF or ET) coupled with an appropriate acceptor. This leads to ET, ET{sup +}, or (ET){sub 2}{sup +} species in the crystal. Using ab initio Hartree-Fock calculations (6-31G** basis set), we show that ET deforms to a boat structure with an energy 28 meV (0.65 kcal/mol) lower than that of planar ET (D{sub 2} symmetry). On the other hand, ET{sup +} is planar. Thus, conduction in this system leads to a coupling between charge transfer and the boat deformation vibrational modes at 20 cm{sup -1} (ET) and 28 cm{sup -1} (ET{sup +}). We suggest that this electron-phonon coupling is responsible for the superconductivity and predict the isotope shifts ({delta}T{sub c}) for experimental tests of the electron-transfer boat-vibration (ET-BV) mechanism. The low frequency of this boat mode and its coupling to various lattice modes could explain the sensitivity of T{sub c} to defects, impurities, and pressure. We suggest that new higher temperature organic donors can be sought by finding modifications that change the frequency and stability of this boat distortion mode. 25 refs., 5 figs., 4 tabs.

Authors:
; ;  [1]
  1. California Inst. of Technology, Pasadena, CA (United States)
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
111206
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 117; Journal Issue: 31; Other Information: PBD: 9 Aug 1995
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; 66 PHYSICS; 99 MATHEMATICS, COMPUTERS, INFORMATION SCIENCE, MANAGEMENT, LAW, MISCELLANEOUS; ORGANIC COMPOUNDS; SUPERCONDUCTIVITY; ELECTRON-PHONON COUPLING; SPECTRAL SHIFT; ORGANIC SUPERCONDUCTORS; BEDT-TTF; THEORETICAL DATA; MOLECULES; ELECTRON TRANSFER; HARTREE-FOCK METHOD; CALCULATION METHODS; VIBRATIONAL STATES; MOLECULAR STRUCTURE

Citation Formats

Demiralp, E, Dasgupta, S, and Goddard, III, W A. Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF. United States: N. p., 1995. Web. doi:10.1021/ja00136a012.
Demiralp, E, Dasgupta, S, & Goddard, III, W A. Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF. United States. doi:10.1021/ja00136a012.
Demiralp, E, Dasgupta, S, and Goddard, III, W A. Wed . "Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF". United States. doi:10.1021/ja00136a012.
@article{osti_111206,
title = {Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF},
author = {Demiralp, E and Dasgupta, S and Goddard, III, W A},
abstractNote = {The highest T{sub c} organic superconductors all involve the organic molecule bis(ethylenedithio)tetrathiafulvalene (denoted as BEDT-TTF or ET) coupled with an appropriate acceptor. This leads to ET, ET{sup +}, or (ET){sub 2}{sup +} species in the crystal. Using ab initio Hartree-Fock calculations (6-31G** basis set), we show that ET deforms to a boat structure with an energy 28 meV (0.65 kcal/mol) lower than that of planar ET (D{sub 2} symmetry). On the other hand, ET{sup +} is planar. Thus, conduction in this system leads to a coupling between charge transfer and the boat deformation vibrational modes at 20 cm{sup -1} (ET) and 28 cm{sup -1} (ET{sup +}). We suggest that this electron-phonon coupling is responsible for the superconductivity and predict the isotope shifts ({delta}T{sub c}) for experimental tests of the electron-transfer boat-vibration (ET-BV) mechanism. The low frequency of this boat mode and its coupling to various lattice modes could explain the sensitivity of T{sub c} to defects, impurities, and pressure. We suggest that new higher temperature organic donors can be sought by finding modifications that change the frequency and stability of this boat distortion mode. 25 refs., 5 figs., 4 tabs.},
doi = {10.1021/ja00136a012},
journal = {Journal of the American Chemical Society},
number = 31,
volume = 117,
place = {United States},
year = {1995},
month = {8}
}