A metal-insulator transition (MIT) in ${\mathrm{BiFeO}}_3$ 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 ${\mathrm{BiFeO}}_3$ at ambient and high pressures were calculated for three experimental crystal structures $R3c$, $Pbnm$, and $Pm\overline{3}m$. 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 $Pm\overline{3}m$ 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 $Pm\overline{3}m$ 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.

• Received 2 March 2015

DOI:https://doi.org/10.1103/PhysRevB.92.035125