Composition and temperature induced changes on the structure of molten ScCl3–CsCl mixtures

Physical Chemistry Chemical Physics Pub Date: 2004-08-03 DOI: 10.1039/B408289C

Abstract

Raman spectroscopy has been used to elucidate the structure of ScCl3–CsCl molten mixtures in the complete composition range and at temperatures up to 1000 °C. The variation of temperature and composition reflected systematic changes in the spectra which were interpreted in terms of structural changes in the melts. In mixtures with ScCl3 mole fractions below 0.5 the melt structure was predominated by a series of ionic species ScCl74?, ScCl63?, Sc2Cl93? and ScCl4? which established different chemical equilibria. At melt compositions rich in ScCl3 the isotropic Raman spectra are characterized by two bands P1 and P2. The position and relative intensities of these bands change with composition in a similar way as observed previously in studies of other rare earth halide systems. Furthermore, the continuous shift of the P2 band with composition is in accordance with the recent computer simulations [P. A. Madden, M. Wilson and F. Hutchinson, J. Chem. Phys., 2004, 120, 6609] which give an understanding of the origin of this band. A cluster-like model is proposed for the structure of molten ScCl3 where fragments of scandium “octahedra” bridged by chlorides are terminated with scandium “tetrahedra” having terminal chlorides.

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