Laser Raman study of phase transitions in [N(CH3)4]2COCl4 single crystals

Abstract

AbstractTemperature‐dependent Raman spectra of oriented single crystals of [N(CH3)4]2CoCl4 are reported. An assignment of the observed Raman bands has been made and it was found that the N(CH3)4+ and CoCl42− groups occupy sites of Cs symmetry in the lattice at room temperature. However, because of rapid reorientation, the CoCl42− groups retain an effective tetrahedral symmetry. The prototypic to incommensurate to commensurate phase transitions are associated with the orientational dynamics of the CoCl4 tetrahedra. The monoclinic to orthorhombic super lattice phase transition at 122 K in [N(CH3)4]2CoCl4 is triggered by the distortion of the N(CH3)4+ groups in the lattice.