Electronic and structural properties of GaN by the full-potential LMTO method : the role of the $d$ electrons

TL;DR

This study uses the full-potential LMTO method to analyze how Ga 3d electrons influence the electronic structure and bonding in cubic GaN, revealing their significant role and unusual features compared to typical III-V compounds.

Contribution

It demonstrates the importance of explicitly including Ga 3d electrons in calculations to accurately describe GaN's electronic and cohesive properties, highlighting its unique behavior among III-V materials.

Findings

Ga 3d electrons strongly influence GaN's band structure.

Unusual valence band features are linked to Ga 3d and N 2s state interactions.

Proper treatment of cation d bands is crucial for accurate properties.

Abstract

The structural and electronic properties of cubic GaN are studied within the local density approximation by the full-potential linear muffin-tin orbitals method. The Ga $3d$ electrons are treated as band states, and no shape approximation is made to the potential and charge density. The influence of $d$ electrons on the band structure, charge density, and bonding properties is analyzed. It is found that due to the energy resonance of the Ga 3$d$ states with nitrogen 2$s$ states, the cation $d$ bands are not inert, and features unusual for a III-V compound are found in the lower part of the valence band and in the valence charge density and density of states. To clarify the influence of the Ga $d$ states on the cohesive properties, additional full and frozen--overlapped-core calculations were performed for GaN, cubic ZnS, GaAs, and Si. The results show, in addition to the known importance of non-linear core-valence exchange-correlation corrections, that an explicit description of closed-shell repulsion effects is necessary to obtain accurate results for GaN and similar systems. In summary, GaN appears to be somewhat exceptional among the III-V compounds and reminiscent of II-VI materials, in that its band structure and cohesive properties are sensitive to a proper treatment of the cation $d$ bands, as a result of the presence of the latter in the valence band range.