Calculation of multipole transitions at the FeK pre-edge through p-d hybridization in the Ligand Field Multiplet model

For the first time, commonly unaccessible local electronic structure parame ters of Fe2+ and Fe3+ in minerals are derived from the calculation of the p re-edge features of X-ray absorption spectra at the Fe K edge. The Ligand F ield Multiplet,lct approach is used to calculate the eigenstates of the ion s and the absolute intensities of the electric-quadrupole and dipole transi tions involved in the pre-edge. For ions in tetrahedral symmetry, a new mod el for p-d hybridization is developed. The degree of admixture between 3d a nd 4p levels is derived and local structure parameters (crystal field, bond covalency) are obtained.