To investigate the different possible surface structures of 13Ns under an ammonia ambient atmosphere, NHx (x=0-3) molecules or radicals were introduced to the surface slab. The NHx species were placed in proximity of possible adsorption sites and the structures were optimized to find stable adsorption configurations. The four different adsorption sites considered, viewed along the (0001) axis, were: top (directly above a metal site), bridge (between two neighboring metal sites), hcp hollow (between three neighboring metal sites, above the top layer nitrogen), and fcc hollow (between three neighboring metal sites, above the empty site in hexagonal packing), see Figure . No adsorbate was found to adsorb to the hcp hollow site, probably due to the close proximity to, and repulsion from, the surface layer nitrogen. As a model for the possible surface after an ideal ALD half cycle, reconstructions were investigated assuming a 1:1 coverage between NHx and surface metal sites if possible. Most of the investigated reconstructions were very similar for the different 13Ns with only small differences in bond lengths and angles, their structures are discussed in the following sections.