On Predicting M枚ssbauer Parameters of Iron-Containing Molecules with Density-Functional Theory
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- 作者：M谩ty谩s P谩pai ; Gy枚rgy Vank贸
- 刊名：Journal of Chemical Theory and Computation
- 出版年：2013
- 出版时间：November 12, 2013
- 年：2013
- 卷：9
- 期：11
- 页码：5004-5020
- 全文大小：724K
- 年卷期：v.9,no.11(November 12, 2013)
- ISSN：1549-9626
文摘
The performance of six frequently used density functional theory (DFT) methods (RPBE, OLYP, TPSS, B3LYP, B3LYP*, and TPSSh) in the prediction of M枚ssbauer isomer shifts(未) and quadrupole splittings (螖E<sub>Qsub>) is studied for an extended and diverse set of Fe complexes. In addition to the influence of the applied density functional and the type of the basis set, the effect of the environment of the molecule, approximated with the conducting-like screening solvation model (COSMO) on the computed M枚ssbauer parameters, is also investigated. For the isomer shifts the COSMO-B3LYP method is found to provide accurate 未 values for all 66 investigated complexes, with a mean absolute error (MAE) of 0.05 mm s<sup>鈥?sup> and a maximum deviation of 0.12 mm s<sup>鈥?sup>. Obtaining accurate 螖E<sub>Qsub> values presents a bigger challenge; however, with the selection of an appropriate DFT method, a reasonable agreement can be achieved between experiment and theory. Identifying the various chemical classes of compounds that need different treatment allowed us to construct a recipe for 螖E<sub>Qsub> calculations; the application of this approach yields a MAE of 0.12 mm s<sup>鈥?sup> (7% error) and a maximum deviation of 0.55 mm s<sup>鈥?sup> (17% error). This accuracy should be sufficient for most chemical problems that concern Fe complexes. Furthermore, the reliability of the DFT approach is verified by extending the investigation to chemically relevant case studies which include geometric isomerism, phase transitions induced by variations of the electronic structure (e.g., spin crossover and inversion of the orbital ground state), and the description of electronically degenerate triplet and quintet states. Finally, the immense and often unexploited potential of utilizing the sign of the 螖E<sub>Qsub> in characterizing distortions or in identifying the appropriate electronic state at the assignment of the spectral lines is also shown.