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 struct ural studies are difficult to perform in cryolite melts because of har d experimental conditions (high temperature, corrosiveness, etc.). Use of the DMol software allows us to determine the stabilities and the v ibrational frequencies of AlF6(3-), AlF5(2-), and AlF4- isolated compl exes. 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 Wi ley & Sons, Inc.