Extended h�ckel calculations of negative spin density

Abstract

Extended Huckel molecular orbital calculations have been performed on the vinyl radical (C2H3·) for a variety of geometries. The net spin densities for the protons have been calculated using a formalism due to McLachlan from the parameters of the Extended Huckel molecular orbital calculations. This calculation includes contributions from the positive spin density at the nucleus and spin polarization contributions, which are weighted by a semi-empirical parameterλ. This is in contrast to the usual Extended Huckel calculation which is incapable of calculating negative spin densities.