Raman spectroscopy in various systems

Systems of metal halides have been extensively investigated by a variety of physicochemical methods and by numerous authors. The reason is the importance of these systems for many important metallurgical processes as well as the systematic investigation of different factors like charge, polarizability, and complexing in monovalent to pentavalent metal halides. A better understanding of molten salts can thus be obtained. 

In the following sections, the results of Raman spectroscopic studies of the systems containing monovalent to tetravalent cations will be presented. 

Raman spectra of alkali metal halide mixtures have also been reported and a detailed analysis was given by Papatheodorou and Dracopoulos (1995) and Papatheodorou et al. (1996). The studies involve systems LiCl-CsCl, LiF-KF, and LiF-CsF and the main findings can be summarized as follows. 

The dramatic increase of the isotropic scattering intensity with increasing temperature is associated mainly with the Li-X interactions and the symmetry of the local stmctures. Thus, increasing the temperature strengthens the short-range overlap interactions and increases the local symmetry around the anion both effects facilitate break-like fluctuations of the polarizability and lead to an increasing isotropic scattering intensity. 

These findings provided a consistent picture of the investigated systems and helped in separating different interaction-induced polarizability mechanisms. Furthermore, the analysis pointed out the important role of the local structure symmetry around the anion to the variation of the isotropic scattering intensity with composition and temperature. 

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