A revised analysis of ferrihydrite at liquid helium temperature using Mössbauer spectroscopy

This dataset contains data which accompanies a research paper (Byrne & Kappler 2022, https://doi.org/10.2138/am-2021-7802) which addresses inconsistencies in the fitting of Fh and provide a more standardized approach to its identification by MBS. Using this data, we presented a systematic comparison of different fitting methods, notably based on Lorentzian and Voigt functions. We suggest that the most suitable approach to fitting pure Fh at liquid helium temperature is with two sextets (A and B) fitted using an extended Voigt based function with the ability to apply probability distributions to each hyperfine parameter. 2-Line Fh: A (δ =0.49 mm/s; ε = 0.00 mm/s; Bhf = 50.1 T) and B (δ = 0.42 mm/s; ε = -0.01 mm/s; Bhf = 46.8 T) 6-Line Fh: A (δ = 0.50 mm/s; ε = -0.03 mm/s; Bhf = 50.2 T) and B (δ = 0.40 mm/s; ε = -0.05 mm/s; Bhf = 47.1 T). We interpret the two sextets to be due to either differences in the coordination environment of iron, i.e., in tetrahedral or octahedral sites, the presence of a disordered surface phase, or a combination of both.