Non-local kinetic energy functional from the Jellium-with-gap model: applications to Orbital-Free Density Functional Theory

TL;DR

This paper introduces a new non-local kinetic energy functional for orbital-free DFT based on the jellium-with-gap model, improving accuracy for semiconductors and metals by incorporating band gap dependence.

Contribution

The paper develops a simple, band gap-dependent non-local KE functional (KGAP) that outperforms previous models, especially for semiconductors.

Findings

KGAP performs better than SM for semiconductors.

KGAP matches accuracy of complex density-dependent functionals.

In the zero-gap limit, KGAP reduces to the SM functional.

Abstract

Orbital-Free Density Functional Theory (OF-DFT) promises to describe the electronic structure of very large quantum systems, being its computational cost linear with the system size. However, the OF-DFT accuracy strongly depends on the approximation made for the kinetic energy (KE) functional. To date, the most accurate KE functionals are non-local functionals based on the linear-response kernel of the homogeneous electron gas, i.e. the jellium model. Here, we use the linear-response kernel of the jellium-with-gap model, to construct a simple non-local KE functional (named KGAP) which depends on the band gap energy. In the limit of vanishing energy-gap (i.e. in the case of metals), the KGAP is equivalent to the Smargiassi-Madden (SM) functional, which is accurate for metals. For a series of semiconductors (with different energy-gaps), the KGAP performs much better than SM, and results are close to the state-of-the-art functionals with complicated density-dependent kernels.