  The grain boundaries, GBs, of corundum Cr2O3 are known to play an important
role in the diffusion of ions within the oxide, which is an important
phenomenon for the corrosion of the stainless steels. The extent of the growth
of oxide layers in stainless steel depends upon which interfaces are preferred
within Cr2O3. Therefore, we have constructed four different grain boundary
planes (rhombohedral, basal, prismatic and pyramidal) and their various
associated interface symmetries known in literature for corundum Al2O3. Their
structural, electronic, and energetic properties are investigated theoretically
with periodic calculations using the DFT+U approach. We find that the prismatic
screw GB with a Cr-O plane interface is the energetically preferred GB with the
rhombohedral GB with screw symmetry and Cr vacancy termination being the second
energetically preferred GB. The increase of the number of in-plane Cr atoms at
the interface of prismatic GB enhances the stability which is also evident in
the electronic density of states.
