Kinetic energy functionals for molecular calculations

The orbitals and eigenvalues of a Kohn-Sham density functional theory calculation can be used to determine the kinetic potential, the functional derivative of the non-interacting kinetic energy. Thus, approproximate kinetic energy functionals can be systematically parameterized to improve their functional derivatives. Fitting procedures have been applied to various functional forms and the quality of the resulting functionals investigated using variationally optimized densities. The best functionals include the full correction of Weizsäcker and a modulation of the Thomas-Fermi p^5/3 term by a function of the distance from the nucleus. These atom-specific functionals predict virtually exact shell structure, and may be combined readily into a functional which supports molecular binding.