To showcase the effectiveness of the GAPW implementation for extended systems, we investigated the V N N B defect in hBN, in which a nitrogen occupies a boron site and a neighboring nitrogen site is missing, as visualized in Figure . Tran et al. show that the weak interaction between hBN sheets has minimal impact on the properties of the defect, therefore we opted for a single-layer hBN. The monolayer hBN unit cell was replicated to a multiple cell of 7 × 4 × 1 and the monolayer was padded with vacuum in z-direction to obtain a simulation box of volume 17.60 × 17.42 × 30 Å 3 . Computations were performed using the HSE06 functional, which is broadly used in studies of semiconductor defects providing bandgaps in agreement with experimental observations. An open-shell electronic configuration was implied to describe the vacancy appropriately. Shifting from highest-accuracy assessments of molecules to a large-scale application, the computational setup was furthermore adjusted: A MOLOPT basis of triple-ζ quality was used as primary orbital basis set. Exact exchange contributions are accelerated using ADMM, requiring an additional auxiliary basis of double-zeta quality. The plane-wave grid cutoff was set to 320 Ry.