Mössbauer Spectroscopy of Iron Carbides: From Prediction to Experimental Confirmation

The Mössbauer spectroscopy of iron carbides (α-Fe, γ'-FeC, η-Fe(2)C, ζ-Fe(2)C, χ-Fe(5)C(2), h-Fe(7)C(3), θ-Fe(3)C, o-Fe(7)C(3), γ'-Fe(4)C, γ''-Fe(4)C, and α'-Fe(16)C(2)) is predicted utilizing the all electron full-potential linearized augmented plane wave (FLAPW) approach across various functionals from LDA to GGA (PBE, PBEsol, and GGA + U) to meta-GGA to hybrid functionals. To validate the predicted MES from different functionals, the single-phase χ-Fe(5)C(2) and θ-Fe(3)C are synthesized in experiment and their experimental MES under different temperature (from 13 K to 298 K) are determined. The result indicates that the GGA functional (especially, the PBEsol) shows remarkable success on the prediction of Mössbauer spectroscopy of α-Fe, χ-Fe(5)C(2) and θ-Fe(3)C with delocalized d electrons. From the reliable simulations, we propose a linear relationship between B(hf) and μ(B) with a slope of 12.81 T/μ(B) for iron carbide systems and that the proportionality constant may vary from structure to structure.