Mossbauer Spectroscopy of Iron Carbides: From Prediction to Experimental Confirmation

The Mossbauer spectroscopy of iron carbides (alpha-Fe, gamma-FeC, eta-Fe2C, zeta-Fe2C, chi-Fe5C2, h-Fe7C3, theta-Fe3C, o-Fe7C3, gamma'-Fe4C, gamma ''-Fe4C, and alpha'-Fe16C2) 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 chi-Fe5C2 and theta-Fe3C 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 Mossbauer spectroscopy of alpha-Fe, chi-Fe5C2 and theta-Fe3C with delocalized d electrons. From the reliable simulations, we propose a linear relationship between B-hf and mu(B) with a slope of 12.81 T/mu(B) for iron carbide systems and that the proportionality constant may vary from structure to structure.