Fig. 3: Coordination numbers from the empirical potential structure refinement fits.

a Average Fe-O coordination number n_FeO in molten FeO_x at 1973 K, 1873 K, 1773 K, 1673 K, and 1573 K (colored symbols) from our EPSR models, as a function of Fe³⁺/ΣFe. n_FeO was determined by the average of three cut-off criteria. The solid gray stars represent crystalline iron oxides. n_FeO obtained by reanalyzing Waseda’s data¹⁰ is shown as the open orange star. n_FeO in molten Fe₂SiO_4+x²⁵ is indicated by the dashed line, as derived from peak fitting to X-ray diffraction data, which may lead to a smaller effective radial cut-off than used herein. b Average n_Fe2+O (open squares) and n_Fe3+O (solid circles) in molten FeO_x at 1973 K (red) and 1673 K (blue). c Average O-Fe coordination number n_OFe in molten FeO_x at 1973 K (red circles) and 1673 K (black triangles) from our EPSR models. The estimated error bars are ±10 Fe³⁺/ΣFe (%) and ±0.25 on the n_FeO or ±0.25(c_Fe/c_O) for n_OFe.