were 𝐸 𝑁 𝑛 𝐻 𝑚 (𝑎𝑑𝑠) is the energy of the adsorbed species per site, 𝐸 𝑣𝑎𝑐𝑎𝑛𝑡 is the energy of the vacant surface per site and 𝐻 2 (𝑔) and 𝐸 𝑁 2 (𝑔) is the energy of hydrogen and nitrogen molecules in gas phase. As the energy is given per surface site Equation 4 was used to calculate the electronic energy (ΔadsE elec ), enthalpy (ΔadsH°), free energy (ΔadsG°) and heat capacity (Δadscp) of adsorption. The calculated energies are listed in Table . The free energies from Table shows that at STP the most preferred structure is the on top adsorbed NH2 for all 13Ns. For InN, the bridging NH2 is almost as stable as the top adsorbed NH2. The smaller difference in energy of the two NH2 terminations for InN compared to AlN and GaN might stem from the larger distance between the neighboring groups causing the hydrogen bond formed to become elongated and weakened, not stabilizing the surface as much as for AlN and GaN.