Single crystals of ThO2, UO2, and their solid solutions, UxTh1–xO2, have been obtained through various hydrothermal growth conditions. This technique offers the better of two other growth processes: (i) single crystal purity as by photochemical growth of nanocrystals; and (ii) large/bulk sizes as obtained by the arc melt method. The band gap of the UxTh1–xO2 single crystal solid solution, along with the luminescence transition, have been characterized. The occupied and unoccupied structures are determined using ultraviolet and inverse photoemission spectroscopy and the electronic band gap was measured to be 3–4 eV. The strain of incorporating U into the ThO2 is analyzed through Vegard's law. In this crystal there are defect and impurity sites, likely arising from the kinetic growth process, giving rise to a similar yet slightly different optical gap evident with cathodoluminescence spectroscopy. There is a major luminescence feature spanning the range from 3.18 to 4.96 eV (250–390 nm) with a maximum at 4.09 eV (303 nm), corresponding with the measured electronic band gap. In this paper, the electronic properties of a solid solution U0.22Th0.78O2 are measured and interpreted compared to the pure actinide oxides, ThO2 and UO2.

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Microstructural and paleopiezometric analyses help constrain conditions and mechanisms of deformation of the Buck Creek ultramafic complex in southwestern North Carolina. Previous work has determined that the complex is an emplaced fragment of partially subducted ocean crust that experienced anhydrous prograde metamorphic conditions to about 800˚C and 1.0 GPa. Twelve olivine-rich dunite/troctolite samples from the Buck Creek ultramafic complex are the focus of this study. Previous work with electron backscatter diffraction (EBSD) shows that the olivine crystallographic preferred orientation (CPO) patterns are generally consistent with axial-[100] or D-type fabric formed under moderate to high stresses with low water content. Axial fabrics may also result from non-plane strain conditions (e.g. constriction or flattening).

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