Arguably, the toughest functional to approximate is the noninteracting Kinetic Energy, $T_{s}[\rho]$. The typical paradigm is to first approximate the energy functional, and then take its functional derivative, $\frac{\delta T_{s}[\rho]}{\delta \rho(r)}$. In this work, we construct the potential from the second-functional derivative and the energy from the potential by functional integration.  The second-functional derivative is constructed to satisfy two exact conditions: (1) the existence of a “kinetic electron” arising from the existence of the exchange hole; (2) for homogeneous densities, the second functional derivative is the inverse Lindhard function. In our pilot calculations, the functional is capable of reproducing Kohn–Sham DFT equilibrium volumes, bulk moduli, phase energy ordering and electron densities of bulk metals and semiconductors. It can also reproduce the energy and density of Magnesium metal clusters of random structure in a 50 eV total electronic energy window. We also compute Fukui functions of these metal clusters and show that they constitute a net improvement compared to previously formulated kinetic energy functionals. This work sets the stage for employing orbital-free DFT in studies of chemical reactivity.

Accurate Fukui functions of finite systems by orbital-free DFT

256th National Meeting (2018)

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