Our choice of exchange-correlation functional for standard calculations is PBEsol, which generally performs well for solids. We use double-ζ basis sets optimized from molecular calculations (MOLOPT) and Goedecker-Teter-Hutter pseudopotentials available within CP2K. We use five multigrids with a relative cutoff of 50 Ry and the finest grid having a cutoff of 500 Ry. CP2K is highly efficient when sampling only the Γ-point, so it is necessary to converge the size of the supercell in order to achieve proper reciprocal space sampling. are in good agreement with reported experimental results. For the PDOS and partial charge density plots at each of the GBs, we use hybrid DFT functional HSE06 to improve the band gaps and charge localization. The computational cost of hybrid calculations is reduced by the CP2K implementation of the auxiliary density matrix method (ADMM) in which exchange integrals are approximated through mapping onto smaller, more localized basis sets.