Spin-orbit and spin-polarization effects in neptunium hexafluoride

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Abstract
Relativistic molecular orbital calculations in the multiple scattering approximation are reported for NpF6, and the results are used to calculate the molecular g tensor and hyperfine parameters for the Np and F nuclei. Core spin-polarization effects are estimated from quasirelativistic spin-unrestricted calculations, which are corrected in an approximate fashion for the effects of spin-orbit mixing. The calculated results (with experimental values in parentheses) are: g=−0.700 (−0.604); A(237Np)=−2.02 GHz (−2.00); a∥(19F)=−103 MHz (−132); and a⊥(19F)=−43 MHz (−42). These results are among the first nonempirical calculations of magnetic resonance parameters for actinide complexes. The calculations predict that the unpaired electron in NpF6 has 4% to 5% fluorine p character.