Some aspects of new orthonormality-constrained orbital optimisation technique

Abstract

The performance of a orthonormality-constrained orbital optimisation procedure has been investigated in its one-configuration limit and compared with that of the traditional method of Roothaan. An intrinsic superiority of the method is manifested in the achievement of smooth and stable optimisation even in pathological cases where Roothaan's method fails to converge. A simple "scaling" technique, somewhat akin to the "damping" procedure of Saunders et al. is developed to enhance the rate of descent on the energy surface. The possibility of generating localized Hartree-Fock orbitals directly by using the new method has also been explored and successfully implemented.