Temperature-pressure phase diagrams were constructed between 200-1800 K and 0.001-1 bar total pressure to model a large set of possible conditions, containing the expected temperatures and pressures during CVD and ALD. A ratio of 1000:1 between gas and adsorption sites was used as an estimation of a surface covered by a free-flowing gas. The initial amount of NH3 compared to N2 in the gas was set to 2:15 and the surface was assumed initially to be bare. quickly increases as temperature is increased and then taper of slowly as it is increased even more, Figure . The maximum coverage of H(tp) is pressure dependent and varies from around 10 % at 1 mbar to 20 % at 1 bar. At low temperatures, the surface is covered by a phase only consisting of NH2(tp). This phase is stable up to 600 K at 1 mbar total pressure to around 700 K at 1 bar. Increasing the temperature above this phase transition line the surface switches to a phase containing H(tp) and bare sites as well as NH2(tp). In a small transition region between those two phase-regions, there is a phase which does not contain any bare sites. The NH2(tp), H(tp) and bare site phase is stable up to 800 K at 1 mbar to 1100 K at 1 bar. Higher temperatures cause NH2(tp) termination to no longer be a favored termination and the surface becomes covered by a mixture of H(tp) and bare sites. At the highest temperature and lowest pressures all adsorptions become unfavorable, and the surface becomes bare. There is a small region of intermediate temperatures (900-1000 K) and high pressure (> 0.5 bar) where the surface A limitation of the equilibrium model is that it predicts the full decomposition of NH3 into N2 and H2 at higher temperatures. According to recent kinetic simulations, this decomposition is too slow to occur during CVD or ALD . This would lead to a too low amount of NH3 in the gas and change the surface phase diagrams. To solve this problem additional pseudoequilibrium calculations were performed with N2 excluded from the possible decomposition products of NH3. N2 is kept as a carrier gas and is allowed to adsorb as N2 dimers but not decompose or abstract hydrogen.