Ab initio study on phase transition and magnetism of BiFeO₃ under pressure

In this paper the first-principles calculations within local spin density approximation (LSDA)+U show that BiFeO₃ experiences a mixed phase state with P4mm structure being the intermediate phase before the pressure of phase transition is reached. The critical pressure for the insulator--metal transition (IMT) is found to be about 50 GPa. A pressure induced crossover of high-spin states and low-spin states is observed close to the IMT pressure in R3c structure. The LSDA+U calculations account well for the mechanism of the IMT and crossover of spin states predicted in recent experiment (Ref.1).