Comprehensive Characterization of the Electronic Structure of U4+ in Uranium(IV) Phosphate Chloride

Emerald-green single crystals of U(PO4)Cl were grown by chemical vapor transport in a temperature gradient (1000 ->-> 900 degrees C). The crystal structure of U(PO4)Cl (Cmcm, Z = 4, a = 5.2289(7) angstrom, b = 11.709(2) angstrom, c = 6.9991(8) angstrom) consists of a three-dimensional network of [PO4] tetrahedra and bicapped octahedral [(UO6Cl2)-O-IV] groups. Polarized absorption spectra measured for two perpendicular polarization directions show a large number of well-resolved electronic transitions. These transitions can be fully assigned on the basis of a detailed ligand-field treatment within the framework of the angular overlap model. The magnetic behavior predicted on the basis of the spectroscopic data is in agreement with an f(2) system and perfectly matched by the results of temperature dependent susceptibility measurements.