Modelling the electronic kinetic energy density and Pauli potential by orbital free density functional theory.

In Kohn Sham density functional theory, the kinetic energy (KE) functional is described by fictitious Kohn-Sham (KS) orbitals. This causes a computational bottleneck for large systems that require many KS orbitals. Much recent research is going into Orbital-Free Density Functional Theory (OFDFT), which models the Kinetic Energy as a functional of density and other ingredients that are derived from density directly, avoiding the need for orbitals. There are reasonable OFDFT models for Kinetic Energy at the meta-GGA level, such the Perdew-Constantin model [1], that properly treat the nonnegativity constraint for the Pauli contribution to the KED, which describes the correction to the von-Weizsäcker KED, which describes the KE of a single electron pair. However, an issue arises of Pauli potentials that are not physically reasonable and difficult to find convergent solutions for. Our goal is to construct meta-GGA level models with potentials which vary smoothly. We test them against calculations of the exact Kohn-Sham KE density and potential for atoms, with atomic densities constructed from the fhi98PP code. As another design goal we will try to incorporate the calculation of linear response.
[1] J. P. Perdew and L. A. Constantin, Phys. Rev. B 75, 155109 (2007).