A Novel Generalized Gradient Approximation for the Non-interacting Kinetic Energy Density Functional

Reliable and accurate approximation of the non-interacting kinetic
energy density functional (KEDF) remains a challenge for extensive
usage of orbital-free density functional theory (OF-DFT). A major
potential OF-DFT application is inexpensive calculation of the electronic
forces in ab initio molecular dynamics (AIMD). We propose a
novel generalized gradient approximation (GGA) non-interacting KEDF in
the context of AIMD, wherein the pseudo-potentials are used
ubiquitously. The sole parameter in the new functional is determined
by imposition of the rigorous Pauli potential positivity constraint
for pseudo-atoms. In static lattice tests on simple solids the new
functional outperforms the previous best constraint-based single-point
functional, VT84F (Phys. Rev. B 88, 161108(R) (2013)). VT84F
satisfies the constraint for Kato densities but not pseudo-densities.
The new functional also does quite well in comparison with
parametrized two-point functionals.