Comments on "Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory" [Appl. Phys. Lett. 89, 161919 (2006)]

TL;DR

This paper critiques previous density functional theory (DFT) calculations of InN and GaN band gaps, clarifying that some local density approximation (LDA) results were accurate and addressing misconceptions about DFT's limitations.

Contribution

The authors clarify that certain LDA calculations correctly predicted properties of InN and GaN, countering claims of DFT limitations in these materials.

Findings

Some LDA calculations accurately described electronic properties.

Previous DFT limitations were overstated.

Successful LDA calculations solved the Kohn-Sham equations self-consistently.

Abstract

An oversight of some previous density functional calculations of the band gaps of wurtzite and cubic InN and of wurtzite GaN by Rinke et al. [Appl. Phys. Lett. 89,161919, 2006] led to an inaccurate and misleading statement relative to limitations of density functional theory (DFT) for the description of electronic properties of these materials. These comments address this statement. In particular, they show that some local density approximation (LDA) calculations have correctly described or predicted electronic and related properties of these systems [Phys. Rev. B 60, 1563, 1999; J. Appl. Phys. 96, 4297, 2004, and 97, 123708, 2005]. These successful calculations solved self-consistently the system of equations defining LDA, i.e., the Kohn-Sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states.