First-principles predictions of low-energy phases of multiferroic BiFeO$_3$

We used first-principles methods to perform a systematic search for potentially stable phases of multiferroic BiFeO3 . We considered a simulation cell compatible with the atomic distortions that are most common among perovskite oxides and found a large number of local minima of the energy within 100 meV/f.u. of the ferroelectric ground state. We discuss the variety of low-symmetry structures discovered, as well as the implications of these findings as regards current experimental (e.g., on thin films displaying supertetragonal phases) and theoretical (on models for BiFeO3's structural phase transitions) work on this compound.