Smearing with σ = 0.1 eV, and an energy cut-off of 400 eV. The convergence criteria were 1x10 -4 eV for the energy minimisation and 0.02 eV/ Å for the forces in the ionic relaxations. We also ran ab initio molecular dynamics (aiMD) calculations for Cu 4 and Cu 29 adsorbed on doped TaN in the NVT ensemble (constant number of particles, N, constant volume, V, and constant temperature, T) with the following inputs: the kinetic energy cutoff is 250 eV; temperature is 500 K. A time step of 5 fs and a total of 1000 steps were used to achieve a total simulation time of 5 ps. The starting geometries used were the optimised structures from the static relaxations, however the atoms in the bottom two layers of the surface slab were frozen for all aiMD calculations.