  In this work an overall electronic structure including the position and
formation energies of various intrinsic defects are computed for anatase using
Density Functional Theory aided by Hubbard correction (DFT+U). The intrinsic
point defects considered here are, oxygen vacancy ($V_O$), oxygen interstitial
($O_i$), titanium vacancy ($V_{Ti}$) and titanium interstitial ($Ti_i$). Out of
all the intrinsic defects considered here, $V_{Ti}$ and $Ti_i$ are found to be
most stable under equilibrium condition. Whereas, conduction band in anatase is
consisted of mainly Ti 3d with a minor component of O 2p states, valence band
is found to be mainly composed of O 2p with a minor contribution from Ti 3d
states. $V_O$ and $Ti_i$ are found to form localized states in the band gap.
Moreover, anisotropy in the effective mass is seen. Finally, an alignment of
band diagrams for all the intrinsic defect states is performed using vacuum
potential from slab-supercell calculation as reference. This first principle
study would help in the understanding of defect-induced insulating to
conducting transition in anatase, which would have significant impact in the
photocatalytic and optoelectronic area.
