Constraint-based, Single-point Approximate Kinetic Energy Functionals

We work toward the development of orbital-free density functionals for the Kohn-Sham kinetic energy $T_s$ of a quality suitable for the computation of quantum-mechanical forces in multi-scale molecular dynamics simulations. The functionals are based on constraints applicable to the Pauli potential $v_\theta=\delta T_\theta/\delta n$, where $T_s=T_w+T_\theta$ and $T_w$ is the von Weizs\"acker kinetic-energy functional. We review our progress to date, and exhibit functionals that do not generate spurious singularities and that produce chemical bonding in semi-quantitative agreement with Kohn-Sham computations and relevant experiments.