  We systematically investigated native defects and reconstructions of TiO2
anatase (101) using USPEX and VASP codes. For lightly reduced samples, the
coverage of O vacancies at surface depends on its concentration in bulk, while
Ti interstitials prefer to dissolve in bulk. Atomic configurations of
reconstructed TiO2 anatase (101) structures were given for severe reduced
samples at the first time. Increasing the reduction degree, the Fermi level can
be modulated in the whole bandgap. For O-rich samples, due to the
indirect-to-direct bandgap transition and bandgap narrowing, O interstitials
are responsible for visible light photoactivity. In a word, stoichiometry
deviations of TiO2 anatase (101) have broad implications for photocatalytic
reactions.
