LAUSR

Abstract Effect of O2 adsorption on the magnetism of the rutile TiO2 (001) surface under different O2 coverages were investigated. The surfaces that we considered for O2 adsorption included the defect-free surface and the O-deficient surfaces with the charge states of 0, +1 and +2. Nonmagnetic defect-free surface is difficult to absorb the O2 molecule. Stabilities of oxygen vacancies with various valences at the top layer depend on their charge states, and the magnetic of the defective surface is related to VO+ instead of VO0 and VO2+. At low O2 coverage, the endothermic adsorptions of O2 molecule may introduce a nonzero local magnetic moment in the neutral reduced surface while its exothermic adsorption cannot. For the +1 or +2 O-deficient surface, the O2 molecule is exothermically adsorbed on the surface and obtains some electrons to form a superoxide anion, which leads to the existence of magnetism. At high O2 coverage, the chemisorptions of new O2 molecule on the neutral O2-preadsorbed substrate are related to the adsorption sites and O O bond oriented. Endothermic adsorption of new O2 molecule induces the magnetic moment on nonmagnetic O2-preadsorbed substrate, while the substrate with the charge state of +1 or +2 inhibits more O2 molecule adsorptions.