A cautionary note on the use of the frozen-core approximation for correlation energy calculations involving alkali metals
✍ Scribed by Heinz Hofmann; Elke Hünsele; Timothy Clark
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 275 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0192-8651
No coin nor oath required. For personal study only.
✦ Synopsis
Test calculations have shown that correlation energies calculated using the frozen-core approximation in programs, such as the Gaussian series, that assume the lowest MOs to be the core orbitals may be significantly in error. Some valence orbitals in systems involving the heavier alkali metals and electronegative elements have lower energies than the highest core orbitals of the metal and are therefore erroneously omitted from the correlation energy calculation. Some examples are discussed.
'A1 AND 'Bz K: ETHYLENE COMPLEXES
There are two low-lying states for the complex between the potassium atom and ethylene, the 2A1 structure, 3, and the 2Bz radical ion pair, 4.