RAMAN-SPECTROSCOPIC STUDY OF MOLTEN ZNBR2-MBR (M=LI, NA) MIXTURES

Raman spectra of molten ZnBr2-MBr (M=Li, Na) systems contained strongl y polarized peaks at about 173 cm(-1) and 148 cm(-1) These were identi fied as the totally symmetric stretching vibration modes of tetrahedra l monomer ZnBr42- and its dimer Zn2Br73-, respectively. The dimers exi sting in the ZnBr2-rich mixture melts tended to be converted into mono mers with increasing alkali bromide concentration or a rise of tempera ture. The ab initio molecular orbital calculations through the Gaussia n program were also performed to check the existence of ZnBr42- monome r and to analyze the vibrational modes of its tetrahedron, the bands o f which were assigned to nu(1), nu(2), nu(3), and nu(4) at 146.6, 51.9 , 177.0, and 82.4 cm(-1), respectively. (C) 1998 Elsevier Science S.A.