Reproducible density functional theory predictions of bandgaps for materials

Even though reproducible computational procedures for density-functional-theory (DFT) calculations of molecular properties are well established, the additional complexities for calculations of materials properties present significant current issues. Considering a randomly selected set of 340 3D materials, we demonstrate that standard computational protocols lead to c. a. 20 % occurrences of significant failures during bandgap calculations. The bandgap is a quintessential materials property that underpins the prediction of most other properties. Examined herein 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. For the pseudopotential and the cutoff energy, optimization of internal computational parameters is performed. For the Brillouin-zone integration, a new computational protocol is developed that chooses grids by minimization of interpolation errors using the second-derivative matrix of the orbital energies. This is shown to provide significant enhancement over established procedures that seek merely to maximize integration-grid densities.