Accurate ⁵⁷Fe Mössbauer Parameters from General Gaussian Basis Sets

Area of Science:

• Computational Chemistry
• Materials Science
• Spectroscopy

Background:

• Accurate prediction of isomer shifts in ⁵⁷Fe Mossbauer spectra typically requires specialized basis sets for density functional theory (DFT) calculations.
• Current methods rely on the precise value of electron density at the nucleus, which can be computationally demanding.

Purpose of the Study:

• To develop a more accessible and accurate method for predicting ⁵⁷Fe Mossbauer isomer shifts.
• To evaluate the performance of integrated nuclear density versus point density in DFT calculations.

Main Methods:

• Utilized density functional theory (DFT) with the conventional def2-TZVP basis set.
• Replaced the nuclear density value with the density integrated within a 0.06 atomic unit (au) sphere around the ⁵⁷Fe nucleus.
• Analyzed a dataset of 69 ⁵⁷Fe-containing compounds (103 signals).

Main Results:

• Achieved excellent calibration lines (r² = 0.976) and high predictive power (q² = 0.975, MAE = 0.055 mm·s^-1) using integrated nuclear density.
• Demonstrated that the B3LYP functional significantly outperforms the PW91 functional for this application.

Conclusions:

• Integrating nuclear density is a viable and effective alternative to using the point density at the nucleus for predicting ⁵⁷Fe Mossbauer isomer shifts.
• This simplified approach enhances the accessibility of accurate Mossbauer spectral predictions using standard computational chemistry tools.