Reliable Density Functional Theory Predictions of Bandgaps for Materials

TL;DR

This study evaluates the accuracy of density functional theory methods for predicting bandgaps in 3D materials, emphasizing the importance of optimized computational parameters to reduce errors.

Contribution

Introduces a k-space optimization scheme that improves bandgap prediction reliability across different functionals and computational settings.

Findings

Cost-saving calculations often lead to significant errors exceeding 0.1 eV.

Unoptimized Brillouin-zone integrations are unreliable for a notable fraction of materials.

The k-space optimization scheme reduces errors, making PBE0 calculations more dependable.

Abstract

We consider methods for optimizing the bandgap calculation of 3D materials, considering 340 sample materials. Examined are the effects of the choice of the pseudopotential to describe core electrons, the plane-wave basis set cutoff energy, and the Brillouin zone integration. Cost-saving calculations in which the structure is optimized using reduced-quality Brillouin zone integrations and cutoff energies were found to lead to experimentally significant errors exceeding 0.1 eV in 18% of cases using the PBE functional and 21% of cases using PBE0. Such cost-savings approaches are therefore not recommended for general applications. Also, the current practice of using unoptimized grids to perform the Brillouin-zone integrations in bandgap calculations is found to be unreliable for 16% of materials using PBE and for 23% using PBE0. A k-space optimization scheme is introduced that interpolates extensive PBE results to determine a generally useful approach that when used in PBE0 calculations is found to be inadequate for only 1.6% of the materials studied.