Mössbauer Spectroscopy and Its Chemical Applications

Abstract

Self-consistent field and charge molecular orbital (MO) calculations are applied to a series of fluorine-, chlorine-, bromine-, and iodine-containing molecules. Calculated orbital energies and dipole moments are used for testing and comparing the MO theories. The calculation procedures for deriving (1) electron charge densities ρ(O), (2) electric field gradient tensors, and (3) internal magnetic fields are described in detail. In connection with calculated ρ(O) values and measured isomer shifts δ, the relative change of nuclear charge radius, δR/R, is derived for iodine. Together with the various contributions to the electric field gradient, the quadrupole polarization of electronic cores γ(r) and thenuclear quadrupole moments Q for chlorine, bromine, and iodine are discussed. For one specific compound, N(C2H5)4-FeI4, the internal magnetic fields at the iron and iodine nuclei are evaluated simultaneously from the magnetic MO structure of this compound. All calculated data are compared with experimental results.