In the present work the methods of relativistic quantum chemistry have been applied to a number of small systems containing heavy elements, for which relativistic e ects are important. First, a thorough introduction of the methods used is presented. This includes some of the general methods of computational chemistry and a special section dealing with how to include the e ects of relativity in ...

Treatment of [NaUN*(C,N)(2)] [N* = N(SiMe(3))(2); C,N = CH(2)SiMe(2)N(SiMe(3))] with I(2) led to the formation of the larger metallacycle [UN*(N{SiMe(3)}SiMe(2)CH(2)CH(2)SiMe(2)N{SiMe(3)})I] resulting from U-C cleavage and C-C coupling. Reaction of [NaUN*(O,N)(2)] [O,N = OC(=CH(2))SiMe(2)N(SiMe(3))] with I(2) afforded the U(V) complex [Na{UN*(O,N)(2)}(2)(μ-I)] which was converted into the monon...

A combination of EXAFS, transmission electron microscopy and energy-dispersive X-ray was used to conduct a molecular and atomic analysis of the uranium complexes formed by Acidithiobacillus ferrooxidans. The results demonstrate that this bacterium accumulates uranium as phosphate compounds. We suggest that at toxic levels when the uranium enters the bacterial cells, A. ferrooxidans can detoxify...

The reported optical constants of uranium differ from that of vacuum significantly more than other elements do over the range of about 150 to 350 eV. This suggests that uranium could be used to produce high reflectance imaging mirrors for many soft x-ray applications. Elemental uranium is too chemically active to be used as a front surface mirror without protection. We computed the expected ref...

The synthesis and spectroscopic characterization of the mononuclear uranium complex [((ArO)(3)tacn)U(III)(NCCH(3))] is reported. The uranium(III) complex reacts with organic azides to yield uranium(IV) azido as well as uranium(V) imido complexes, [((ArO)(3)tacn)U(IV)(N(3))] and [((ArO)(3)tacn)U(V)(NSi(CH(3))(3))]. Single-crystal X-ray diffraction, spectroscopic, and computational studies of thi...

We compare results of measurements of magnetization, specific heat, electrical resistivity and neutron diffraction on single crystals and oriented polycrystalline powders of various UTX compounds. Very strong anisotropy, persisting also in the paramagnetic state, is a general feature of these materials. Compounds with the hexagonal ZrNiAl-type structure exhibit, as a rule, a uniaxial anisotropy...

The reaction chemistry of uranium metal has been well documented for use in the development of nuclear fuels. The oxidation of uranium from the thermal stress of nearby combustion is different than that of a reactor environment due to the selectivity of the various competing reactions. This work extracts available information in literature and various experiments over the last 60 years to provi...

optic properties of uranium-based compounds" Uranium-based compounds often show interesting magnetic properties and large polar Kerr rotations. Because of this, the wavelength and temperature dependencies of the polar Kerr rotation in several uranium-based compounds, including UMnzGez, UFe2, and UGa2, have been investigated. The Mn moments order ferromagnetically in UMnzGel below 380 K, and whi...

Several elements (V, Mo, Fe, Mn, Cd, Zn) as metallic impurities in pure uranium compounds were quantitatively determined by atomic absorption spectrometry. The effects of uranium and that of other factors on the absorption intensity of each element were studied. The analyzed samples were dissolved in 6 M nitric acid, and uranium was selectively extracted with tributylphosphate. The aqueous solu...

We review here the magnetic properties of some strongly correlated electron systems and especially cerium and uranium compounds. The normal Kondo lattice model with a localized S = 1/2 spin can account for the Kondo-magnetism competition observed in cerium or ytterbium systems, while the underscreened Kondo lattice model with a localized S = 1 spin can well account for the ferromagnetism — Kond...