HEYNS, AM and RANGE, KJ and MULLER, K (1991) THE POLYMORPHISM OF ALKALI-METAL FORMATES .4. A RAMAN-STUDY OF THE PHASE-TRANSITION IN KHCOO. CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 69 (11). pp. 1774-1780. ISSN 0008-4042,
Full text not available from this repository.Abstract
KHCOO II is orthorhombic at ambient conditions and it is shown that traces of moisture affect the polymorphism of these very hygroscopic crystals. Dry KHCOO II transforms into phase I at 417 K (144-degrees-C), and this phase can be supercooled to room temperature, remaining metastable for several days before transforming back to the orthorhombic phase II. The Raman spectra of phases I and II, as well as of supercooled phase I, are reported in the present study. The absence of some prominent translational modes in the Raman spectra of KHCOO II, compared to NaHCOO II, can be explained on the basis of a group-theoretical treatment. From the temperature dependence of the linewidths of various Raman-active librational and internal modes, activation energies are obtained for intramolecular motions of the formate ions. Fermi resonance occurs between the overtone of the bending mode 2-nu-5 and the C-H stretching mode nu-1 in KHCOO II and the coupling constant W increases with temperature. The Raman and X-ray data show that KHCOO I is structurally different from NaCHOO I, but it is not possible to assign a definite structure to this phase on the basis of a Raman spectrum alone.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | SODIUM FORMATE; POTASSIUM FORMATE; LATTICE MODES; ASSIGNMENT; SPECTRUM; NAHCOO; POTASSIUM FORMATE; PHASE TRANSITION; RAMAN SPECTRA |
| Depositing User: | Dr. Gernot Deinzer |
| Last Modified: | 19 Oct 2022 08:46 |
| URI: | https://pred.uni-regensburg.de/id/eprint/54803 |
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