BonnMag a Computer Program for Angular Overlap Modeling of all fⁿ-Systems: New Insights into Ligand-field splitting of Lanthanide and Actinide ions

Abstract

In this thesis the development of the computer program BonnMag is described. By using BonnMag the excited state energies, magnetic susceptibilities and moments can be calculated for all fⁿ systems (1 ≤ n ≤ 13) within the framework of angular overlap model. BonnMag should contain a symmetry analysis of the electronic states (calculation of J projections), assignment of the irreducible representations to the split terms for all thirty two point groups, estimation of the absorption coefficients by using the Judd-Ofelt theory. As test for BonnMag compounds containing Nd³⁺ (f³), Eu³⁺ (f⁶), and U⁴⁺ (f²) have been investigated. Detailed experimental data on different lanthanide and actinide compounds comprising powder reflectance and single-crystal UV/vis/NIR spectra as well as temperature dependent magnetic moments form the basis for the investigation of the electronic structure of the considered ions. The AOM calculations using BonnMag allow separation of ligand-field effects and spin-orbit coupling on the energy of the observed electronic states. Due to the simple and fast procedure a large number of calculations with variation of parameters is possible. Thus, assessment of the "best fit AOM parameters" as well as the transferability of these parameters is accomplished.