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

TY - JOUR

T1 - The spin-unrestricted and the spin-projected HF methods

T2 - a comparison based on the stability properties of the closed-shell RHF solutions for large cyclic polyenes

AU - Castaño, O.

AU - Karadakov, P.

PY - 1986/1/1

Y1 - 1986/1/1

N2 - 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 spin-PHF energy hypersurface.

AB - 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 spin-PHF energy hypersurface.

UR - http://www.scopus.com/inward/record.url?scp=46149140532&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:46149140532

SN - 0009-2614

VL - 130

SP - 123

EP - 126

JO - Chemical Physics Letters

JF - Chemical Physics Letters

IS - 1-2

ER -