MINDO/3 comparison of the generalized SCF coupling operator and “half-electron” methods for calculating the energies and geometries of open shell systems

Abstract

The MINDO/3 semi-empirical SCF MO method has been extended to the generalized coupling operator (GCO) treatment of open shell systems proposed by Hirao and Nakatsuji and has been used to calculate heats of formation and equilibrium geometries of various ground state radicals and the lowest singlet and triplet excited states of a series of closed shell ground state molecules. The results are compared with those from the “half-electron”(HE) method. While the heats of formation calculated by these methods are slightly different, the predicted equilibrium geometries do not differ appreciably. The generalized coupling operator method required more computing time in nearly all cases.