Local Behavior of the First-Order Gradient Correction to the Thomas-Fermi Kinetic Energy Functional

TL;DR

This paper investigates the local behavior of the first-order gradient correction to the Thomas-Fermi kinetic energy functional, demonstrating its accuracy and improved local behavior over traditional semilocal functionals in atomic and model systems.

Contribution

The study provides a detailed evaluation of the first-order gradient correction's local behavior and accuracy, showing its superiority over existing semilocal functionals.

Findings

Low relative errors in total kinetic energy

Better local kinetic energy density behavior

Outperforms usual GGA semilocal functionals

Abstract

The first order gradient correction to the Thomas-Fermi functional, proposed by Haq, Chattaraj and Deb (Chem. Phys. Lett. vol. 81, 8031, 1984) has been studied by evaluating both the total kinetic energy and the local kinetic energy density. For testing the kinetic energy density we evaluate its deviation from an exact result through a quality factor, a parameter that reflects the quality of the functionals in a better way than their relative errors. The study is performed on two different systems: light atoms (up to Z=18) and a noninteracting model of fermions confined in a Coulombic-type potential. It is found than this approximation gives very low relative errors and a better local behavior than any of the usual generalized gradient approximation semilocal kinetic density functionals.