The structure of borate melt has long been a fundamental unsolved problem in condensed matter physics, materials chemistry. Here, we use high temperature Raman spectroscopy and first principles calculations to study the structural change before and after the melting of a BiB 3 O 6 crystal to obtain the BiB 3 O 6 melt structure. A transformation of the 4-fold coordinated boron atoms to 3-fold coordinated boron atoms and a destruction of the atomic configuration around the Bi 3+ ions were found when the crystal melted. Considering the growth habit of the BIBO crystal, we proposed a polymer model for the first time to describe the melt structure
