Phase transition of iron doped MgO under high pressure by first-principles study

Abstract

The ( Mg, Fe ) O solid solution is one of the major lower mantle minerals, and studying its properties and structures under high pressure is a fundamental step toward understanding Earth's deep interior. Here within the framework of density functional theory, we first discuss the relationship between the total energy and iron doped positions of ( Mg, Fe ) O , and find that the doped iron favors to be dispersive. Then the pressure-induced phase transitions of ( Mg, Fe ) O from NaCl -type (B1) to CsCl -type (B2) are probed. It is found that the phase transition pressure of ( Mg, Fe ) O decreases with damped oscillation, as the increase of iron concentration. This phenomenon is essentially determined by the iron concentration as well as iron doped positions. The electronic structures of MgO and ( Mg 0.75 Fe 0.25) O at 436 GPa are calculated, and the results show that the doped irons play a crucial role in the metallicity of ( Mg 0.75 Fe 0.25) O . Our results are in agreement with the experimental counterparts. This study would provide some useful information for understanding the behavior of pressure-induced phase transition and geoscience.