Stress-driven reconstruction of an oxide surface: The anatase TiO₂(001)-(1×4) surface

The recently discovered (1×4) reconstruction of the stoichiometric anatase TiO₂(001) surface is studied via first principles density functional calculations. We propose a new structural model for this reconstruction, which is energetically much more favorable than all the other available models, including the unreconstructed (1×1) surface. In this model, rows of TiO₃ species periodically replace rows of surface bridging oxygens of the (1×1) surface, thus leading to a relief of the large surface tensile stress present on that surface. The corresponding empty-state charge density distribution correctly describes the experimental scanning tunneling microscopy images.