Actual and Idealized Crystal Field Parameterizations for the Uranium Ions in UF4

Abstract The crystal field parameters for the actual coordination symmetries of the uranium ions in UF4, C2 and C1, and for their idealizations to D2, C2v , D4, D4d , and the Archimedean antiprism point symmetries are given. They have been calculated by means of both the perturbative ab initio model and the angular overlap model and are referenced to the recent results fitted by Carnall's group. The equivalency of some different sets of parameters has been verified with the standardization procedure. The adequacy of several idealized approaches has been tested by comparison of the corresponding splitting patterns of the 3H4 ground state. Our results support the parameterization given by Carnall. Furthermore, the parameterization of the crystal field potential and the splitting diagram for the symmetryless uranium ion U(C1) are given. Having at our disposal the crystal field splittings for the two kinds of uranium ions in UF4, U(C2) and U(C1), we calculate the model plots of the paramagnetic susceptibility χ(T) and the magnetic entropy associated with the Schottky anomaly ΔS(T) for UF4.