Pressure-driven metal-insulator transition in BiFeO3 from dynamical mean-field theory

A metal-insulator transition (MIT) in BiFeO3 under pressure was investigated by a method combining generalized gradient corrected local density approximation with dynamical mean-field theory (GGA+DMFT). Our paramagnetic calculations are found to be in agreement with the experimental phase diagram: Magnetic and spectral properties of BiFeO3 at ambient and high pressures were calculated for three experimental crystal structures R3c, Pbnm, and Pm3¯m. At ambient pressure in the R3c phase, an insulating gap of 1.2 eV was obtained in good agreement with its experimental value. Both R3c and Pbnm phases have a metal-insulator transition that occurs simultaneously with a high-spin (HS) to low-spin (LS) transition. The critical pressure for the Pbnm phase is 25-33 GPa, which agrees well with the experimental observations. The high-pressure and -temperature Pm3¯m phase exhibits a metallic behavior observed experimentally as well as in our calculations in the whole range of considered pressures and undergoes the LS state at 33 GPa, where a Pbnm to Pm3¯m transition is experimentally observed. The antiferromagnetic GGA+DMFT calculations carried out for the Pbnm structure result in simultaneous MIT and HS-LS transitions at a critical pressure of 43 GPa in agreement with the experimental data. ©2015 American Physical Society