Raman spectroscopic study of molten ZnBr2–MBr (M=Li, Na) mixtures

Abstract Raman spectra of molten ZnBr 2 –MBr (M=Li, Na) systems contained strongly polarized peaks at about 173 cm −1 and 148 cm −1 . These were identified as the totally symmetric stretching vibration modes of tetrahedral monomer ZnBr 4 2− and its dimer Zn 2 Br 7 3− , respectively. The dimers existing in the ZnBr 2 -rich mixture melts tended to be converted into monomers with increasing alkali bromide concentration or a rise of temperature. The ab initio molecular orbital calculations through the Gaussian program were also performed to check the existence of ZnBr 4 2− monomer and to analyze the vibrational modes of its tetrahedron, the bands of which were assigned to ν 1 , ν 2 , ν 3 , and ν 4 at 146.6, 51.9, 177.0, and 82.4 cm −1 , respectively.