Simulation Package (VASP) with projector augmented wave (PAW) potentials , using the PBE functional . The energy cutoff for the plane waves was chosen as 400.0 eV, and Gaussian smearing with a sigma of 0.1 was used, while the electronic energy convergence parameter was chosen as 10 -6 eV. The D3 dispersion correction was used . The model substrate used was an aalumina(0001) surface with cell parameters of a = 4.807 Å and c = 13.126 Å, previously found to best match the experimental support. The lower layers of the slab were kept fixed during global optimization and subsequent adsorbate binding calculations. Only gamma-point sampling was used due to the larger supercell used in the study.