Electron—molecular-vibration coupling in 7,7,8,8-tetracyano-p-Quinodimethane (TCNQ)

The linear coupling constants describing the interaction of the one-electron molecular orbitals with the molecular vibrations in TCNQ are calculated using a semi-empirical spectroscopically parameterized CNDO molecular orbital model. The cartesian displacements for the normal mode of vibrations are computed on the basis of a modified valence force field (MVFF). The calculated vibrational progressions associated with the highest occupied orbital are in excellent agreement with the observed high resolution photoemission spectrum. The present investigation also confirms the importance of the intramolecular coupling for the description of metal-insulator transitions in TTF-TCNQ. © 1976.