The spin-unrestricted and the spin-projected HF methods: a comparison based on the stability properties of the closed-shell RHF solutions for large cyclic polyenes
✍ Scribed by Obis Castan̄o; Peter Karadakov
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 370 KB
- Volume
- 130
- Category
- Article
- ISSN
- 0009-2614
No coin nor oath required. For personal study only.
✦ Synopsis
Investigations into the stability of the closed-shell RHF solutions for cyclic polyenes of varying ring size have been carried out in the framework of the spin-UHF and spin-PHF methods employing the PPP approximation. With increasing ring size the lowest eigenvalues from the non-singlet stability problem for the two different methods tend to different constant values, while the overlap between the eigenvectors corresponding to these eigenvalues tends to a constant non-unit value. These results show that even for large systems the spin-UHF energy hypersurface does not coincide with the spm-PHF energy hypersurface.