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Study of the Phase Transitions of (DI-DCNQI) 2M ( M=Ag, Li,Cu) through the Analysis of the Temperature-Dependent Vibronic and Vibrational Infrared Absorptions
Ist Teil von
Journal of solid state chemistry, 2002-11, Vol.168 (2), p.632-638
Ort / Verlag
San Diego, CA: Elsevier Inc
Erscheinungsjahr
2002
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
The temperature-dependent phase transitions of 2,5 diiodo-dicyanoquinondiimmine (2,5-DI-DCNQI) title compounds are analyzed by looking at the bond order wave (BOW) and at the charge density wave (CDW) which characterizes the transitions. The analysis is done by studying the temperature-dependent powder infrared spectra which allow one to have a separate evaluation of both types of contribution to the phase transition of these molecular metals. A model for the spectroscopic infrared features related to the transitions is reported and used for the analysis. It is found that all the title compounds develop a BOW structure at low temperatures with characteristics which recall an instability toward a tetramerized 2
k
F
periodicity particularly for the Ag and Li compounds. An appreciable CDW amplitude contribution to the transitions is not found in the spectra.