Vibrational modes and structure of the LaCl3CsCl melts

Raman spectra of the LaCl3CsCl melt mixtures at ten different compositions, including solid and molten LaCl3 have been measured at temperatures up to 900 °C. The systematic spectral changes with composition and the invariance of the spectra on temperature are discussed in terms of the melt structure and in relation to other lanthanide halide–alkali halide melt mixtures. The data suggest that in CsCl-rich mixtures the predominant species present are the LnCl63− “octahedral” while in LaCl3-rich melts a network-like structure of chloride bridged coordination polyhedra is formed. Most likely the predominant coordination of La3+ remains six-fold at all compositions. The reduced isotropic and anisotropic Raman spectra are calculated and compared with the recently published simulated Raman spectra of the same melt mixtures.