Spin-extended Hartree-Fockab initiocalculations for small radicals

Abstract
The unrestricted Hartree-Fock method and its spin-projected and spin-extended versions are used for calculating the model correlation energy and isotropic and anisotropic hyperfine splitting constants for LiH+, BeH, BH+ and OH radicals. Results are compared with those of the method of complete configuration interaction. The gradient method of Murtagh and Sargent is employed for direct minimization of EHF electronic energy.