Adsorption of single metal atoms (Cu, Co, and Ru) on TaN was explored to have an initial evaluation of the binding energy between the metals and the substrate. These results are also used to benchmark the calculations against previous studies. Six non-equivalent adsorption sites on TaN were considered for the metal adatoms, shown in Figure . At four of the sites (A, B, D, and F) the metal adatom bridges two nitrogen atoms, while at the remaining two sites (C and E) the adatom sits on top a nitrogen atom. 14 All three metal adatoms are unstable at the E site after relaxation, where they move onto a neighbouring D (Cu and Co) or A (Ru) site during the relaxation. In addition, the Ru adatom was also not stable on the C site, where it migrated to an F site during the relaxations. All other sites were stable for the adatoms. The instability of a Ru adatom at the C and E sites could be explained by the low coordination number of the adatom at these sites, as it only binds to a single nitrogen atom.