Minimizing propagated density errors of atomic core-electron for simultaneously accurate bandgaps and lattice constants in closed-shell copper semiconductors

Density functional theory struggles to accurately determine the electron density of atoms, whose error is inevitably encoded into the pseudopotential and propagated into solid-state calculations. However, little is known about how this affects accuracy nor how to remedy it. In this work, through a systematic study of the effect of Cu atomic density on bandgap and lattice constants of over 50 Cu-containing simple closed-shell semiconductors, we find that core-electron density can drastically affect nuclear attraction to valence electrons and subsequent charge distribution and energy position of Cu 3d electrons. The error can be eliminated at its source by employing modified Hartree-Fock pseudopotentials for the Cu core while retaining (semi-)local functionals for valence electrons. This real-space partitioning approach leads to simultaneous high accuracy in bandgap and lattice constants across the entire material class.