Raman- und IR-messungen an den perchloraten von Kalium, Rubidium und Caesium in den orthorhombischen tieftemperaturmodifikationen (baryt-typ) und in den kubischen Hochtemperaturphasen (NaCl-Typ mit orientierungsfehlordnung der ClO−4-Ionen)
1983; Pergamon Press; Volume: 39; Issue: 1 Linguagem: Inglês
10.1016/0584-8539(83)80046-4
ISSN1873-3824
AutoresH. D. Lutz, Robert A. Becker, W. Eckers, Brigitte G. Hölscher, H. J. Berthold,
Tópico(s)Ionic liquids properties and applications
ResumoZusammenfassung The i.r. and Raman spectra of the anhydrous perchlorates KClO 4 , RbClO 4 , and CsClO 4 have been recorded in the temperature range 90—600 K, i.e. in both the orthorhombic baryte-type low-temperature modifications and the cubic NaCl-type high-temperature forms with orientationally disordered ClO − 4 ions. The perchlorates under investigation exhibit unusually fast cation exchange in alkaline halide discs. The assignment of the modes was made with the help of Raman single crystal measurements. From site group and unit cell group splitting of the internal ClO − 4 modes it is shown that in the baryte-type perchlorates deviation from T d symmetry of the ClO − 4 ions is considerably smaller and interionic interaction of the vibrations significantly larger than in the anhydrite-type sodium perchlorate [20]. The frequency shifts of the internal ClO − 4 modes within the series KClO 4 , RbClO 4 , and CsClO 4 and of ClO − 4 ions trapped in KBr and RbBr matrixes are discussed in terms of the repulsion potential of the lattice. The spectra of the cubic high-temperature modifications indicate full T d symmetry of the ClO − 4 ions in these compounds.
Referência(s)