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Orbital-free density functional theory (OF-DFT) constitutes a computationallyhighly effective tool for modeling electronic structures of systems rangingfrom room-temperature materials to warm dense matter. Its accuracy criticallydepends on the employed kinetic energy (KE) density functional, which has to besupplied as an external input. In this work we consider several nonlocal andLaplacian-level KE functionals and use an external harmonic perturbation tocompute the static density response at T=0 K in the linear and beyond linearresponse regimes. We test for the satisfaction of exact conditions in the limitof uniform densities and for how approximate KE functionals reproduce thedensity response of realistic materials (e.g., Al and Si) against the Kohn-ShamDFT reference which employs the exact KE. The results illustrate that severalfunctionals violate exact conditions in the UEG limit. We find a strongcorrelation between the accuracy of the KE functionals in the UEG limit and inthe strongly inhomogeneous case. This empirically demonstrates the importanceof imposing the limit of UEG response for uniform densities and validates theuse of the Lindhard function in the formulation of kernels for nonlocalfunctionals. This conclusion is substantiated by additional calculations forbulk Aluminum (Al) with a face-centered cubic (fcc) lattice and Silicon (Si)with an fcc lattice, body-centered cubic (bcc) lattice, and semiconductingcrystal diamond (cd) state. The analysis of fcc Al, and fcc as well as bcc Sidata follows closely the conclusions drawn for the UEG, allowing us to extendour conclusions to realistic systems that are subject to densityinhomogeneities induced by ions.

Imposing Correct Jellium Response Is Key to Predict the Density Response by Orbital-Free DFT