Detailed experimental data on UPO₄Cl comprising single-crystal UV/vis/NIR spectra and temperature-dependent magnetic susceptibilities form the basis for the investigation of the electronic structure of the U⁴⁺ cation in UPO₄Cl. For modeling of the observed physical properties the angular overlap model (AOM) was successfully employed. The computations were performed using the newly developed computer program BonnMag. The calculations show that all electronic transitions and the magnetic susceptibility as well as its temperature dependence are well-reproduced within the AOM framework. Using Judd–Ofelt theory BonnMag allows estimation of the relative absorption coefficients of the electronic transitions with reasonable accuracy. Ligand field splitting for states originating from f-electron configurations are determined. Slater–Condon–Shortley parameters and the spin–orbit coupling constant for U⁴⁺ were taken from literature. The good transferability of AOM parameters for U⁴⁺ is confirmed by calculations of the absorption spectra of UP₂O₇ and (U₂O)(PO₄)₂. The effect of variation of the fit parameters is investigated. AOM parameters for U⁴⁺ (5f) are compared to those of the rare-earth elements (4f) and transition metals (3d)
