Universal alignment of defect thermodynamics in hematite

Abstract

Abstract First-principles defect calculations in hematite ( α -Fe 2 O 3 ) suffer from a &gt;2 eV spread in reported formation energies, arising from (i) metastable or delocalized charge states and (ii) inconsistent error cancellation with chemical-potential boundaries across studies. We introduce a charge-localization protocol based on the Fe-3 d occupation matrix that enforces physically meaningful small-polaron configurations and eliminates the spurious loss of intermediate charge states; the resulting thermodynamic charge-transition levels are essentially independent of computational parameters. To establish a common energy scale, we use the crossing point of the fully ionized Frenkel pair ( $${V}_{{\rm{Fe}}}^{3-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Fe</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> and $${{\rm{Fe}}}_{i}^{3+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mi>Fe</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>i</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> ) as an intrinsic anchor and align the chemical potentials to parameter-independent experimental formation enthalpies. This reduces the inter-study deviation by ~80%, and reveals that the remaining absolute shifts are dominated by VBM displacement amplified by the large nominal defect charges. The framework provides a reproducible benchmark for hematite defect energetics and is directly transferable to other correlated oxides.