Approach to Orbital-Free DFT with Englert-Schwinger model

Orbital-free density functional theory (OFDFT) is a variant of DFT which tries to circumvent construction of Kohn-Sham orbitals in order to efficiently scale to larger system sizes. Most of the research on OFDFT is on improving the accuracy of the non-interacting kinetic energy T_s[n] approximation as a direct functional of density, which requires use of pseudopotentials. Instead of density functionals, we focus on potential functional formalism. This formalism allows us to sidestep use of pseudopotentials and directly use atomic orbitals alongside orbital-free functionals. We assess the self-consistent performance of potential functionals by Englert and Schwinger. Specifically we compare the Englert-Schwinger model to Kohn-Sham and Thomas-Fermi-Dirac-Weizsäcker models self-consistently on small systems, especially atoms showing that the potential functionals by Englert and Schwinger are a viable alternative to the non-interacting kinetic energy density functionals. We also present the augmentation of this model with Kohn-Sham orbitals, which allow us to explore OFDFT solution without the use of pseudopotentials.