  We use \textit{ab initio} calculations to estimate formation energies of
cation (transition metal) antisite defects at oxide interfaces and to
understand the basic physical effects that drive or suppress the formation of
these defects. Antisite defects are found to be favored in systems with
substantial charge transfer across the interface, while Jahn-Teller distortions
and itinerant ferromagnetism can prevent antisite defects and help stabilize
atomically sharp interfaces. Our results enable identification of classes of
systems that may be more and less susceptible to the formation of antisite
defects and motivate experimental studies and further theoretical calculations
to elucidate the local structure and stability of oxide interface systems.
