Descriptive analysis of the crystal structure of the 1-D semiconducting TCNQ salt : TEA(TCNQ)2, as a function of temperature. - I. Intermolecular distortions of the conducting TCNQ columns

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Abstract
Within reasonable approximations, the structure of a conducting TCNQ column is characterized by six parameters. Two parameters define the equivalent regular column, and four parameters refer to the intermolecular distortions. Two of the distortional parameters are associated with a dimerization in the column, while the other two parameters are associated with a tetramerization. It is then shown, as an experimental fact, that only two of these six parameters are significantly temperature dependent. The first one simply accounts for the usual thermal expansion of the column. The second one is associated with a component of the tetramerization perpendicular to the column axis. The possible implications of these findings with respect to the semiconducting properties of the material are also discussed. In complement to the present article, a second one will concern an analysis of the charge distribution on the TCNQ molecules of a conducting column