Electron-intramolecular vibration coupling in TTF-TCNQ systems

Abstract

We report calculations of the linear electron molecular vibration coupling constants in TCNQ, TCNQ−, and TTF. A complete neglect of differential overlap (cndo) type parameterization is used for the electronic structure and a modified valence force field (mvff) approach for the determination of the vibrational normal modes. Direct experimental information on the magnitude of the coupling constants can be obtained in the gaseous phase from photoemission experiments and in the solid state from polarized optical reflectance measurements on organic linear chain conductors. Agreement between theory and experiment is good. The relevance of electron-intramolecular vibrational coupling constants for the stabilization of the charge density wave (cdw) state in TCNQ anion radical salts and in the determination of polaron binding energies is stressed.