Kinetic energy density functional based on electron distribution on the energy coordinate to describe covalent bond

TL;DR

This paper introduces a new kinetic energy functional based on electron distribution on the energy coordinate, successfully describing covalent bonds and overcoming limitations of traditional models like TF and GGA.

Contribution

A novel KEF utilizing electron distribution on the energy coordinate is developed, enabling accurate modeling of covalent bonds in DFT.

Findings

Successfully models covalent bonds in H₂ molecule

Demonstrates the KEF captures static correlation effects

Introduces potential gradient correction method

Abstract

The development of kinetic energy functional (KEF) is known as one of the most difficult subjects in the electronic density functional theory (DFT). In particular, the sound description of chemical bonds using a KEF is a matter of great significance in the field of theoretical physics and chemistry. It can be readily confirmed that the famous Thomas-Fermi (TF) model or the TF model corrected with a generalized gradient approximation (GGA) fails to realize the bound state of a covalent bond in general. In this work, a new kinetic energy functional is developed on the basis of the novel density functional theory (J. Phys. B: At. Mol. Opt. Phys. 51, 055102, 2018) that utilizes the electron distribution on the energy coordinate as the fundamental variable. It is demonstrated for an H$_2$ molecule that the bound state can be realized by the KEF by virtue of the property of the electron density on the energy coordinate. The mechanism underlying the formation of the bound state is the same as that for the realization of the static correlation in the exchange energy described with the new DFT. We also developed a method termed potential gradient method to make a correction to the TF model instead of the GGA approach.