Generalized spin orbital calculations of spin-frustrated molecules

It is difficult to consider the closed chain which contains odd‐number spin sites under the UHF approximation because of the spin frustration. The generalized HF (GHF) method, which deals with generalized spin orbitals (GSO) of the form ϕαα+ϕββ, can provide a characteristic electronic state with noncollinear spin configuration. In this article, explicit expressions of effective exchange integrals ( Jab values) based on GHF solutions were derived for the closed chain which contains odd‐number spin sites. The Jab values were calculated for simple systems such as equilateral triangular H3, equilateral pentagonal H5, and so on. Furthermore, spin correlations and electron correlations of the H3 molecule are discussed by using visualization methods for electron correlations. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001