Hartree-fock roothaan calculations using optimized huzinaga orbitals on small molecules

Abstract

We present the ground-state solution of some small molecules using the Hartree–Fock Roothaan method with the optimized Huzinaga basis set. Unlike the previously used least-square methods, the contraction coefficients and exponents of Huzinaga-parameterized primitive Gaussian functions for minimal basis sets are energy-optimized at the atomic level for each molecule. Consequently, as an alternative to and in comparison with standard parameterization, the optimized orbitals significantly improve the total energy and the equilibrium bond length with substantial enhancement shown for heavier nuclei. Despite similar computational cost, the application of our scheme leads to much improved minimal-basis-set Hartree–Fock calculations with less required parameters to match the large basis set calculations. Furthermore, the localization of the electrons near the nuclei which is missing with the standard parameterization is observed with the current scheme.