Adsorption of Au on an O-deficient MgO(001) surface

The atomic and electronic properties of the O-deficient MgO(001) surface and effects of Au adsorption (0.25 monolayer) are investigated using the full potential linearized augmented plane wave method. The calculated formation energy of a surface (bulk) O vacancy on MgO(001) is 9.5 eV (10.0 eV). The vacancy induces gap states in a range of 1.8-3.3 eV above the valence band, which is expected to strongly alter the chemical properties of MgO(001). Through total energy and atomic force calculations, the adsorption of Au on the ideal MgO(001) surface is found to be very weak with a Au-O bond length (d(Au-O)) of 2.16 Angstrom and an adsorption energy (E-ad) of -0.13 eV/adatom. On the defective MgO(001) surface, Au adatoms prefer the vacancy sites with a strongly enhanced adsorption energy of -1.93 eV/adatom. The core state energies of Au 4f(7/2) are very sensitive to the change of environment.