GEOMETRICAL AND SPECTROSCOPICAL CHARACTERIZATIONS OF SOME COMPLEX ENTITIES OF ALUMINUM(III) WITH FLUORIDE IONS BY LDF-BASED CALCULATIONS

The structure of cryolite is investigated with a theoretical approach based on LDF calculations. In fact, experimental techniques for structural studies are difficult to perform in cryolite melts because of hard experimental conditions (high temperature, corrosiveness, etc.). Use of the DMol software allows us to determine the stabilities and the vibrational frequencies of AlF6(3-), AlF5(2-), and AlF4- isolated complexes. The results obtained compared with published experimental works confirm that AlF5(2-) should be considered in the dissociation scheme of cryolite as previously evidenced by other authors. (C) 1994 John Wiley & Sons, Inc.