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Keywords:

  • ferropericlase;
  • Hubbard potential;
  • spin states

Abstract

An iron-related high-to-low spin transition in ferropericlase, (MgFe)O, has been identified at high pressures. Since this is one of the major minerals of Earth's lower mantle, and the respective transition occurs at mantle pressure and temperature conditions, this transition could have important geophysical implications. Here, we performed a theoretical investigation on the properties of a substitutional iron impurity in magnesium oxide, (MgO: FeMg), and the respective changes with increasing isotropic pressure. This microscopic configuration represents the limiting case of absent iron–iron interactions in ferropericlase, which allowed us to explore the magnetic properties of the isolated iron center. The calculations were performed using the WIEN2k package, within the density functional theory plus a Hubbard potential correction. The structural, electronic, and magnetic properties of those centers at several charge states and pressures (up to 100 GPa) were compared. We also discussed the possibility of an iron-related intermediate spin (IS) state in ferropericlase. Our results on the quadrupole splitting indicate that such IS state should have properties similar to the respective spin state in ferrosilicate perovskite.