Prediction of ⁵⁷Fe Mössbauer Parameters by Density Functional Theory: A Benchmark Study

Abstract

We report the performance of eight density functionals (B3LYP, BPW91, OLYP, O3LYP, M06, M06-2X, PBE, and SVWN5) in two Gaussian basis sets (Wachters and Partridge-1 on iron atoms; cc-pVDZ on the rest of atoms) for the prediction of the isomer shift (IS) and the quadrupole splitting (QS) parameters of Mössbauer spectroscopy. Two sources of geometry (density functional theory-optimized and X-ray) are used. Our data set consists of 31 iron-containing compounds (35 signals), the Mössbauer spectra of which were determined at liquid helium temperature and where the X-ray geometries are known. Our results indicate that the larger and uncontracted Partridge-1 basis set produces slightly more accurate linear correlations of electronic density used for the prediction of IS and noticeably more accurate results for the QS parameter. We confirm and discuss the earlier observation of Noodleman and co-workers that different oxidation states of iron produce different IS calibration lines. The B3LYP and O3LYP functionals have the lowest errors for either IS or QS. BPW91, OLYP, PBE, and M06 have a mixed success whereas SVWN5 and M06-2X demonstrate the worst performance. Finally, our calibrations and conclusions regarding the best functional to compute the Mössbauer characteristics are applied to candidate structures for the peroxo and Q intermediates of the enzyme methane monooxygenase hydroxylase (MMOH), and compared to experimental data in the literature.

Mössbauer parameters of organometallic compounds and polarizability effect

“…Hence the isomer shift is linearly proportional to the electron density at the indicator nucleus. In recent years this conclusion is confirmed by results of DFT calculations of the electron density at the nuclei 57 Fe [49,52], 119 Sn [43], 121 Sb [43,44], 127 I [45], and 197 Au [51].…”

“…We mention in passing that the D value obtained for 57 Fe [49,52], 119 Sn [47,48], 121 Sb [44], and 127 I [45] [53,54] and are at the basis of the correlation analysis. Therefore this investigative techniques are promising in understanding the mechanism for the influence of substituents on the d and D parameters.…”

Insights into the Different Dioxygen Activation Pathways of Methane and Toluene Monooxygenase Hydroxylases

“…40 The B3LYP functional was used to compute the isomer shift whereas O3LYP was the functional of choice for the quadrupole splitting parameter. The completely uncontracted Partridge-1 basis set was placed on the iron atoms, and the conventional cc-pVDZ basis resided on the rest of atoms of the model.…”

Calibration of DFT Functionals for the Prediction of 57Fe Mössbauer Spectral Parameters in Iron–Nitrosyl and Iron–Sulfur Complexes: Accurate Geometries Prove Essential

“…3,17–26 For example, Neese and coworkers have found that fit parameters are relatively insensitive to whether nonrelativistic or quasi-relativistic (via the zero-order regular approximation, ZORA) DFT methods are employed. 22,25 The ZORA Fe electron densities are shifted towards the four-component Dirac–Fock limit, but no improvement in the correlation is observed.…”

“…They found the B3LYP and O3LYP density functionals to have the lowest errors while M06-2X and SVWN5 possess the highest for their large test set of 31 iron-containing complexes (35 signals), including both mononuclear and dinuclear systems. 26 …”