Mössbauer spectroscopy is a key method for investigating structural and electronic properties of iron nuclei in molecular environments, 1 e.g. bioinorganic systems like hemoglobin, P450, and Nitrogenase, molecular complexes and catalysts, or single atom catalysts such as FeNC catalysts for the oxygen reduction reaction. Mössbauer spectroscopy is often used to elucidate structures and electronic structures, usually in combination with density functional theory calculations on known or plausible structures. While Mössbauer spectroscopy -like many other spectroscopiesshows a temperature dependence, quantum chemical calculations are usually restricted to a rigid equilibrium geometry at absolute zero. For Mössbauer spectroscopy, this limits the direct comparison of experiment and theory to experimental temperatures below 77 K, and makes the assignment of signals observed under in situ or operando conditions at higher temperatures significantly less reliable.