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Raman Evidence for a Phase Transition inCdPS 3
Author(s) -
Sourisseau C.,
Cavagnat R.,
Evain M.,
Brec R.
Publication year - 1996
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199602)27:2<185::aid-jrs932>3.0.co;2-g
Subject(s) - raman spectroscopy , monoclinic crystal system , phase transition , ion , stacking , diffraction , crystallite , crystallography , chemistry , phase (matter) , atmospheric temperature range , materials science , analytical chemistry (journal) , condensed matter physics , crystal structure , optics , thermodynamics , physics , organic chemistry , chromatography
Raman spectra (600–10 cm −1 ) of polycrystalline samples of CdPS 3 were investigated over the temperature range 340–100 K. In agreement with recent x‐ray diffraction data, a first‐order transition with large hysteresis effects was characterized between a monoclinic room‐temperature phase ( C 2/ m with one layer) and a trigonal low‐temperature phase ( R 3 with three layers). In particular, upon cooling the translational modes of Cd 2+ ions split into doublets at 130–128 cm −1 ( T′x , y ), 81.5–80 cm −1 ( T′z ) and two new low‐wavenumber ‘rigid layer’‐type modes are detected at 44.5 and 30 cm −1 . This confirms that the phase transition mechanism is governed by an ordering of the Cd 2+ ions and a stacking mode change of the sulphur layers (from CdCl 2 to CdI 2 type) whose interlayer force constants are estimated to be 0.186×10 2 and 0.085×10 2 N m −1 for the compressional and shearing motions, respectively.