Partial dissociation of water on Fe${}_3$O${}_4$(001): adsorbate induced charge and orbital order

The interaction of water with Fe${}_3$O${}_4$(001) is studied by density functional theory (DFT) calculations including an on-site Coulomb term. For isolated molecules dissociative adsorption is strongly promoted at surface defect sites, while at higher coverages a hydrogen-bonded network forms with alternating molecular and dissociated species. This mixed adsorption mode and a suppression of the $(\sqrt{2}\times \sqrt{2})R{45}^{\circ }$-reconstruction are confirmed by a quantitative low energy electron diffraction (LEED) analysis. Adsorbate induced electron transfer processes add a new dimension towards understanding the catalytic activity of magnetite(001).