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Ab Initio Study of the AlX 3 ···2H 2 O (X = F, Cl) and AlF 3 ···3H 2 O Complexes

1997; American Chemical Society; Volume: 101; Issue: 8 Linguagem: Inglês

10.1021/jp962534l

1520-5215

M. Krossner, Gudrun Scholz, Reinhard Stößer,

Molecular Spectroscopy and Structure

The structures, binding energies, and harmonic vibrational frequencies of AlX3···2H2O (X = F,Cl) complexes have been explored for the first time at the HF, DFT, and MP2 levels using the 6-31G*, 6-31+G*, and the 6-311G** basis sets. The optimizations were performed without symmetry restrictions or other structural limitations. All complexes investigated were found to be energetically stable, regardless of the computational method used. The calculations showed that the DFT(B3LYP)/6-31+G* method is suitable for the prediction of both binding energies and vibrational frequencies for these types of complexes. This makes possible qualitatively accurate calculations at a relatively low computational expense of even larger, comparable complexes. The AlF3···3H2O complex was therefore investigated only at this level, yielding the basis for the molecular interpretation of the first steps of the macroscopically investigated hydration process of AlF3. A comparison of the binding energies of complexes containing an increasing number of water molecules has been performed. Furthermore, the vibrational frequencies of all complexes have been predicted.