VII. CONCLUSION P-rich InP(001) was investigated by photoemission spectroscopy as well as DFT calculations. We found a strong surface band bending, which we attributed to hydrogen vacancies, leading to P dangling bonds and induce half filled mid-gap surface states. Low temperature water adsorption could not reveal a strong interaction of the molecular water with the present InP(001) surface. Our computational results could confirm that the considered dangling bond defect does not significantly change the adsorption behavior of the InP(001) surface compared to the hydrogen saturated surface. After the desorption of molecular water, we could only find traces of remaining OH groups at the InP(001) surface, indicating a partial dissociation of the water molecule. Potential-energy surface calculation reveal that in contrast to H 2 O, P dangling bonds strongly change the adsorption behavior of OH, which is able to passivate the mid-gap state after bonding to the dangling bond site. However, the remaining Fermi level pinning after water adsorption indicate that P dangling bonds are not the active sites for water dissociation on P-rich InP(001) surfaces as neighboring active sites for H 2 O cleavage are missing.