| Numéro |
J. Phys. Colloques
Volume 41, Numéro C6, Juillet 1980
THIRD EUROPHYSICS TOPICAL CONFERENCELATTICE DEFECTS IN IONIC CRYSTALS |
|
|---|---|---|
| Page(s) | C6-437 - C6-437 | |
| DOI | https://doi.org/10.1051/jphyscol:19806112 | |
LATTICE DEFECTS IN IONIC CRYSTALS
J. Phys. Colloques 41 (1980) C6-437-C6-437
DOI: 10.1051/jphyscol:19806112
PHASE TRANSITIONS AND EXCITONS
Raman and infrared studies of librational-translational modes in stress-aligned ferroelastic KCN
D. Durand1, 2, L. C. Scavarda do Carmo1, 3 et F. Luty1 1 Physics Department, University of Utah, Salt Lake City, Utah 84112, U.S.A.
2 Physics Department, Université de Metz, France
3 Pontificia Universidad Catolica do Rio de Janeiro, and supported by a fellowship from PUC and CNPg (Brazil)
Abstract
KCN crystals, when cooled from the pseudo-cubic disordered phase into the low temperature phase of parallel CN- order, break up into a multi-domain structure with strong light scattering. As this prevents any measurements of polarized Raman or IR spectra, the assignment of bands to particular librational and/or translational modes has been highly speculative and controversial in previous works. By application of uniaxial stress in the ferroelastic phase, we have succeeded to align a large fraction of the ortho-rhombic domains and to reduce the light scattering. This enabled us, for the first time, to measure polarized spectra of the librational/translational modes, the CN- stretching and combinations of both, using Raman and IR techniques. From experiments with various stress-and light-geometries, the symmetry properties of all observed Raman and IR transition are determined. Definite assignments of these bands to particular librational and translational modes will be presented and discussed.