One of the advantages of interpolated potential is that it is easy to investigate it in detail. counted from the potential minimum, is 1.01 eV in this elbow plot with r = 0.79 Å and Z = 2.04 Å, similar to previous studies. Nudged elastic band calculations as implemented in the atomic simulation environment (ASE) with default parameters were performed to find the minimum energy barrier for recombinative desorption of two H atoms from neighbouring fcc sites in all dimensions (with a rigid surface, however). The minimum barrier is 0.72 eV for r = 0.77 Å and Z = 2.39 Å calculated for the (4 × 4) unit cell, i.e., the barrier is substantially reduced when neighboring H atoms are allowed to rearrange along the reaction pathway. We have checked that the barrier and minimum energy path remains the same for (6 × 6) and (3 × 3) unit cells. As shown in Figure there are also local minima in the minimum energy path at 2 Å for (3 × 3) and (4 × 4) unit cells and at 3 Å for the (2 × 2) unit cell. These minima correspond to situation when two H atoms become close to each other (r≈ 0.8 Å), but still close to the surface (Z≈ 2.7 Å).