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Laser Raman study of phase transitions in [N(CH 3 ) 4 ] 2 COCl 4 single crystals
Author(s) -
Rathore R. P.,
Khatri S. S.,
Chakraborty T.
Publication year - 1987
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/jrs.1250180610
Subject(s) - monoclinic crystal system , raman spectroscopy , orthorhombic crystal system , crystallography , chemistry , lattice (music) , phase transition , tetrahedron , tetrahedral symmetry , crystal structure , condensed matter physics , physics , optics , rotational symmetry , acoustics , mechanics
Temperature‐dependent Raman spectra of oriented single crystals of [N(CH 3 ) 4 ] 2 CoCl 4 are reported. An assignment of the observed Raman bands has been made and it was found that the N(CH 3 ) 4 + and CoCl 4 2− groups occupy sites of C s symmetry in the lattice at room temperature. However, because of rapid reorientation, the CoCl 4 2− groups retain an effective tetrahedral symmetry. The prototypic to incommensurate to commensurate phase transitions are associated with the orientational dynamics of the CoCl 4 tetrahedra. The monoclinic to orthorhombic super lattice phase transition at 122 K in [N(CH 3 ) 4 ] 2 CoCl 4 is triggered by the distortion of the N(CH 3 ) 4 + groups in the lattice.