Studying the effect of different exchange correlation functionals on the structural and electronic properties of a half-Heusler NaAuS compound

TL;DR

This study investigates how different exchange correlation functionals affect the structural and electronic properties of the topological insulator NaAuS, revealing variations in lattice constants, bulk modulus, and band gap with each functional.

Contribution

It provides a comparative analysis of multiple exchange correlation functionals on NaAuS's properties, highlighting their impact on electronic structure predictions.

Findings

Lattice constants range from 6.128 Å to 6.442 Å across functionals.

NaAuS exhibits a direct band gap with spin-orbit coupling, around 0.23-0.26 eV.

NaAuS shows band inversion, confirming its topological insulator nature.

Abstract

Theoretically, NaAuS is predicted as topological insulator, while no detail electronic structure study has been done for this compound. Here, we report the structural and electronic properties of NaAuS by using LDA, PBEsol, PBE and revPBE exchange correlation functionals. The calculated values of equilibrium lattice constant for LDA, PBEsol, PBE and revPBE exchange correlation functionals are found to be $\sim$6.128 {\AA}, $\sim$6.219 {\AA}, $\sim$6.353 {\AA} and $\sim$6.442 {\AA}, respectively. The bulk modulus predicted by LDA, PBEsol, PBE and revPBE exchange correlation functionals is $\sim$66.6, $\sim$56.4, $\sim$46.5 and $\sim$39.3 GPa, respectively. Hence, the order of calculated values of bulk modulus is consistent with the order of calculated values of equilibrium lattice parameters for these exchange correlation functionals. The spread of total density of states below the Fermi level decreases as the exchange correlation functional changes from LDA to PBEsol to PBE to revPBE, which is also found to be consistent with the order of bulk modulus for these exchange correlation functionals. In presence of spin-orbit coupling, a direct band gap is observed in NaAuS compound, which is found to be $\sim$0.26, $\sim$0.25, $\sim$0.24 and $\sim$0.23 eV for LDA, PBEsol, PBE and revPBE exchange correlation functionals, respectively. Here, NaAuS is found to be topological insulator as it shows band inversion at $\Gamma$ point. The calculated values of band inversion strength for LDA (PBEsol) and PBE (revPBE) exchange correlation functionals are $\sim$1.58 eV ($\sim$1.57 eV) and $\sim$1.50 eV ($\sim$1.47 eV), respectively.