Study of the phase transitions of (DI-DCNQI)2X using vibronic and vibrational spectra

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

“…More appropriate for such an analysis are the temperature-dependent sharp features which can be easily identified and do not show strong interference with other spectral features. Looking at the spectra, one finds that the vibronic band at 622 cm À1 , which can be associated to the totally symmetric N-CN bending, is apt for the analysis of the temperature dependent transition as previously found in a preliminary report (16). Figure 3 shows the integrated intensity of this band as a function of temperature normalized to its maximum value.…”

Pattern of charge ordering in quasi-one-dimensional organic charge-transfer solids

“…It was pointed out by the present authors that some of the experimental results, especially the appearance of the CO at a temperature lower than the metal-insulator transition (see Section IV), perhaps indicated the ...1100... order 6 . Initial optical measurements had detected evidence for a 4k F BOW without CO already at room temperature, which had suggested that a ...1100... CO accompanies the second lattice distortion that occurs at lower temperature 8 . A first X-ray structural study found moderately strong satellite intensities in the 4k F phase (10 −3 of the Bragg reflection), accompanied by high l indices 50 .…”

“…Recent experiments 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 showing clear evidence for the existence of charge-order (CO) in several 2:1 cationic organic charge transfer solids (CTS) have stimulated considerable theoretical interest 17,18,19,20,21,22,23,24,25,26 . As these materials are nominally 1 4 -filled (one electron or hole per two sites) and involve electron-electron (e-e) interactions (including nearest-neighbor Coulomb repulsion V ), the apparently obvious charge ordering in the quasi-1D CTS systems is the Wigner crystal-like "...1010..." state, and numerous theoretical 20,26 and experimental 5,12,13,14,15,16 studies have argued for this possibility.…”

Spiral Charge Frustration in the Molecular Conductor(DI−DCNQI)2Ag

“…One is the lattice displacements suggested by optical spectra analyses [13,14]: The IR and Raman spectra are complicated and not well fitted by such simple CO without assuming any lattice distortions. Another unaccountable behavior is seen in the NMR line shape [11].…”