New Submission: Orbital-free density functionals based on real and reciprocal space separation.

We introduce a general class of kinetic energy density functionals (KEDFs) for orbital-free density functional theory (OF-DFT) that can be decomposed into a local part in coordinate space and a local part in reciprocal space. As a demonstration of principle, we choose for the former the Thomas-Fermi-von Weizsacker (TFW) KEDF and introduce for the latter a functional form derived from the Lindhard response function, but with the two adjustable parameters made system-dependent. These parameters are machine-learned from Kohn-Sham data using Bayesian linear regression in conjunction with the kernel method, while employing moments of the Fourier components of the electronic density as the descriptor. Through representative cases of metals and binary alloys, we demonstrate that when the part of the functional that is local in reciprocal space is applied non-self-consistently for frozen phonon calculations, there is more than an order-of-magnitude improvement in the accuracy of the energy relative to the TFW KEDF, with negligible increase in the cost. Overall, this work opens an avenue for the construction of accurate KEDFs for OF-DFT.