Improved Prediction of Mössbauer Quadrupole Splitting at High and Low Temperatures with a Quantum Chemical Ensemble Approach
Year: 2026
Type: preprint
Abstract: Mössbauer spectroscopy is a key method for characterizing the electronic structures of iron compounds. The resulting Mössbauer parameters show a well-established temperature dependence. For quantum chemical calculations that are often used to aid in the interpretation of Mössbauer spectra, this poses a major challenge: they commonly employ a single, rigid equilibrium structure that is assumed to deliver good results for low temperatures up to ca. 80 K. In this work, we reveal this approach to be a rather severe approximation. We use a structural sampling approach that captures the effect of temperature dependent molecular vibrations on the quadrupole splitting. Even for low temperatures, this approach delivers a significantly improved agreement with experimental data. In addition, the T-dependence of the quadrupole splitting can be qualitatively reproduced for four iron(II) high spin complexes. The results are analyzed in terms of the individual EFG tensor contributions, which shows the origin of the temperature dependence being rooted in different electronic structures with varying contributions at different temperatures. Limitations in the sampling approach and electronic structure method are discussed. The approach presented herein may provide better agreement with experiment in future in situ and operando studies at low, ambient and elevated temperatures.
Source: ChemRxiv
Institution: Technische Universität Darmstadt
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223188083