Pressure-driven metal-insulator transition inBiFeO3from 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 experimental phase diagram: Magnetic and spectral properties of BiFeO3 at ambient and high pressures were calculated for three experimental crystal structures R3c, Pbnm and Pm3̄m. 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 that agrees well with the experimental observations. The high pressure and temperature Pm3̄m phase exhibits a metallic behavior observed experimentally as well as in our calculations in the whole range of considered pressures and undergoes to the LS state at 33 GPa where a Pbnm to Pm3̄m 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.