from, and respectively. The vacuum between the slabs was set larger than 13 Å and the dipole correction was applied in z direction. The Brillouin zone was sampled by a Γ-centered 3 × 3 × 1 k-points mesh generated through the Monkhorst-Pack. The gas-phase molecules were relaxed in a cubic box with 20 Å sides. Electronic convergence was set to 1 × 10 -5 eV and atomic positions were converged until residual forces fell below 0.03 eV Å -1 .