Interestingly, the computational findings are very similar for the hydrogen deficient, i.e. the InP(001) 2×2-2D-1H surface. However, compared to water adsorption on the 2×2-2D-2H surface, a slightly larger (by about 0.03 eV) adsorption energy is calculated. The calculated PES indicates again adsorption preferentially in the trench between the P dimer rows (Fig. (right)). Here, the H 2 O molecule bonds weakly to the P dimer, which is partially H saturated. For that reason, the electronic mid-gap state resulting from H desorption is not affected by water adsorption, confirming our experimental results, according to which no electronic nor chemical reactions could be identified upon the adsorption of molecular water.