Vibrational frequencies of AlF3: An ab initio MO study evaluating different methods on a tricky case
✍ Scribed by Gudrun Scholz; Klaus Schöffel; Vidar R. Jensen; Øystein Bache; Martin Ystenes
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 596 KB
- Volume
- 230
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
The vibrational frequencies of AIF, have been calculated with ab initio methods at the Hartree-Fock level, at correlated levels (MP2, QCISD, MCSCF) and with the LDF method including local (LSD) and non-local spin density (NLSD) functions. The basis set sensitivity was examined with a large number of basis sets including polarization and diffuse functions. The calculations do not confirm the assignment of u4 to 263 cm-', but suggest a frequency of -240 cm-' for this mode. The u, mode most probably is close to 670-675 cm-'. The lowest recommendable level for vibrational analysis of AlF,, and probably also for related species, seems to be HF/6-3 1 + G*.
' Anionic species in lattices or melts cannot be described exactly quantum mechanically by assuming that they are free ions. Some authors therefore regard these ions merely as fictions (e.g. see last comments in Ref. [ 241). On the other hand, several works have dealt successfully with quantum mechanical predictions of vibrational frequencies of such anions, although the deviations normally become larger with increasing charges (see Ref.