Structure and dynamics of concentrated aqueous solutions of aluminium chloride, beryllium chloride and aluminium bromide: Raman, inelastic neutron scattering and x-ray diffraction results

Structural and dynamical investigations on concentrated aqueous solutions of aluminium chloride and bromide in liquid and glassy states have been performed by means of Raman and inelastic neutron scattering spectroscopy and by x-ray diffraction. Inelastic neutron scattering results for solutions of beryllium chloride in a glassy state are compared with the results for the aluminium cation solutions. Isotopic changes on going from H₂O to D₂O of the Raman spectra assigned to vibrations of water molecules in the cation hydration shells are discussed. Inelastic neutron scattering data complement and corroborate the Raman spectral study. Further structural information is obtained from x-ray diffraction experiments, and its interpretation is supported by calculations based on ad hoc molecular models. The existence of a liquid-type quasi-close packing is suggested for concentrated aqueous solutions of aluminium halides, in agreement with previous studies.