High temperature Raman spectroscopic study of the micro-structure of a caesium triborate crystal and its liquid

Raman spectra of a caesium triborate (CBO) crystal at different temperatures up to the melting temperature have been recorded. All of the peaks of corresponding to the crystal broaden and decrease in wavenumber with increasing temperature. The vibrational modes of the CBO crystal, in which the basic structural unit is the triborate group (B3O7)5-, have been simulated using a plane-wave pseudopotential method. An isomerization reaction from four-coordinated boron to a three-coordinated species was observed during the melting process. The continuous three-dimensional network of the crystal collapsed and transformed into spiral chains that consist of (B3O6)3- groups during the melting process. Detailed spectral analysis is also competently explained by applying quantum chemistry ab initio calculations.