X-ray study of the anion ordering transition in di (tetramethyltetraselenafulvalen)-ium perchlorate (TMTSF)2ClO4 : quenching and irradiation effects

R. Moret , J.P. Pouget , R. Comès , K. Bechgaard

We report the results of an X-ray diffraction study of the phase transition of (TMTSF)2ClO4 at 24 K. The influence of the cooling rate is evaluated by its effect on the intensity and width of the superstructure reflections appearing at the transition. We also report important irradiation effects on this anion ordering transition, previously unobserved in other compounds of the (TMTSF)2X family. The superstructure reflection intensities are strongly reduced and the transition temperature is lowered upon X-ray irradiation. Partial annealing of the irradiation induced disorder is observed The intensities of 220 superstructure reflections were measured and a preliminary analysis shows that anion ordering accounts for most of the intensity. We conclude that distortions of the TMTSF backbone at the transition are minor (in contrast to the features previously reported for (TMTSF)2ReO 4).

Mots clés: order disorder transformations; organic compounds; quenching thermal; X ray diffraction examination of materials; X ray effects

Domaines: Articles anciens

R. Moret, J.P. Pouget, R. Comès, K. Bechgaard. X-ray study of the anion ordering transition in di (tetramethyltetraselenafulvalen)-ium perchlorate (TMTSF)2ClO4 : quenching and irradiation effects. Journal de Physique, 1985, 46 (9), pp.1521-1532. ⟨10.1051/jphys:019850046090152100⟩. ⟨jpa-00210098⟩