Interpretation of the 57Fe Isomer Shift by Means of Atomic Hartree–Fock Calculations on a Number of Ionic States

Abstract

The Hartree-Fock method is used to calculate the values of 1 'l'(0) I' for a number of configurations of different Fe ions. An interpolation formula for 1 'l'(0) I' as a function of the occupation number of valence electron orbitals (3d, 4s, 4p) is given. Experimental Mossbauer isomer shifts are correlated to estimated configurations which are compared to available MO calculations for a few cases.

First principles calculation of Mössbauer isomer shift

“…Because of the negative fractional charge radius R/R of 57 Fe, the increase in the contact density results in a negative isomer shift. In this way, an interpolation formula for the isomer shift ␦ as a function of the (fractional) occupation numbers of the atomic valence orbitals was designed and parametrized on the basis of comparison with the experimental data [114,115].…”

Calibration of computational Mössbauer spectroscopy to unravel active sites in FeNC catalysts for the oxygen reduction reaction

“…To translate the parameters predicted by DFT into those derived experimentally and assess the reliability of the DFT prediction, calibration studies for various combinations of density functionals, basis sets, grid sizes, relativistic options, and solvation and dispersion corrections exist alongside very early work based on Hartree-Fock (HF) theory. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] Given this wealth of information, the reasons for presenting another calibration study may not be obvious. Our motivation to calibrate computational Mössbauer spectroscopy is 3-fold: (a) several technical advances have been made that are not included in previous calibration studies, for example, newer basis sets, approximations, and corrections; (b) some of the more recent studies do not report on the quadrupole splitting; [19,24] (c) the emergence of single-atom catalysts, where the catalytically active iron site is embedded in an ill-defined carbonaceous environment with significant π-character, [8] presents a challenging problem for computational Mössbauer spectroscopy and hence warrants a dedicated assessment of its predictive power for this specific coordination environment.…”

Charged State ofFe57Atoms Following the Decay ofCoMicklitz1, Barrett2 1972Phys. Rev. Lett.47010View full textAdd to dashboardCite

“…Nonrelativistic Hartree-Fock calculations 16 give for the difference in the nonrelativistic total electron density at the iron nucleus, ^2(0), between the atomic configurations The IS difference between the rare-gas-matrixisolated Fe and FeF 2 , together with this new AR/ R value, gives for the difference in ^2(0) between Fe and FeF 2 the value 7.35 ±0.25 a.u. The difference in ^2(0) between Fe(3d 6 4s 25 D) and Fe 2+ (3d 6 5 D) as obtained in Ref.…”