Structure and dynamics of molten aluminium and gallium trihalides

Abstract

Results of Raman scattering experiments combined with ab initio molecular orbital calculations are presented on the structure and vibrational properties of molten GaI₃, GaBr₃, AlCl₃, and AlBr₃. It is confirmed that, to a high degree, all of these compounds have in the molten state a dimer structure, represented by M₂X₆, consisting of two tetrahedra sharing a halide edge. It is shown that in AlCl₃ the melting process leads to a drastic change in the vibrational spectrum, whereas in the remaining salts the crystalline peak positions are essentially preserved.