Comment on "Calibration of ⁵⁷Fe Mössbauer constants by first principles" Phys. Chem. Chem. Phys., 2016, 18, 10201–10206

The proportionality constant, α, between the observed isomer shifts and the calculated electron probability density at the iron nucleus has been reevaluated in terms of the correct experimental isomer shifts relative to α-iron and their corresponding accuracy, which should be considered in the linear regression fit yielding α. The iron-57 excited state nuclear quadrupole moment, Q, is not a "relative" value and its widely accepted experimental value is 0.16(1) × 10 ^-28 m ² as also confirmed by nuclear model calculations.