We present a systematic comparison of the lattice structures, electronic density of states, and band gaps of actinide dioxides, AnO(2) (An=Th, Pa, U, Np, Pu, and Am) predicted by the Heyd-Scuseria-Ernzerhof screened hybrid density functional (HSE) with the self-consistent inclusion of spin-orbit coupling (SOC). The computed HSE lattice constants and band gaps of AnO(2) are in consistently good agreement with the available experimental data across the series, and differ little from earlier HSE results without SOC. ThO(2) is a simple band insulator (f(0)), while PaO(2), UO(2), and NpO(2) are predicted to be Mott insulators. The remainders (PuO(2) and AmO(2)) show considerable O2p/An5f mixing and are classified as charge-transfer insulators. We also compare our results for UO(2), NpO(2), and PuO(2) with the PBE+U, self interaction correction (SIC), and dynamic mean-field theory (DMFT) many-body approximations.

Transport behavior of monovalent and divalent solutes across mesoporous Anopore γ-alumina membranes was investigated as a function of pore diameter, pH, ionic strength, and nature of the salt or complexing species in solution. Radiotracers 137 Cs, 85 Sr, 22 Na, and 45 Ca were present in the feed solutions at very low concentrations, ranging from 10 -9 to 10 -12 M and total salt concentrations from 0.1 to 10 -4 M. The divalent cations Ca 2+ and Sr 2+ exhibit lower diffusion rates (3-7 times slower) than the monovalent cations Cs + and Na + for membranes with 20 nm diameter pores. Differences between monovalent and divalent cation diffusion rates for the membranes can be explained in terms of a Donnan exclusion effect from the positively charged alumina surface. The rate of Sr 2+ transport across the 20 nm alumina membranes was greatly increased by raising the pH (reducing the membrane surface charge) from 5 to 8 for both the feed and receive sides. Increased ionic strengths and the addition of complexing agents or specific salt solutions also facilitated divalent ion transport. Diffusion coefficients for divalent cations increased 3-fold for the 100 nm pore diameter membranes.

We report a solution based synthesis of epitaxial thin films of neptunium oxide and plutonium oxide. Actinides represent a challenge to first principle calculations due to features that arise from f orbital interactions. Conventional semi-local density functional theory predicts NpO 2 and PuO 2 to be metallic, when they are well known insulators. Improvements in theory are dependent on comparison with accurate measurements of material properties, which in turn demand high-quality samples. The high melting point of actinide oxides and their inherent radioactivity makes single crystal and epitaxial film formation challenging. We report on the preparation of high quality epitaxial actinide films. The films have been characterized through a combination of X-ray diffraction and X-ray absorption fine structure (XANES and EXAFS) measurements. We report band gaps of 2.80 6 0.1 eV and 2.85 6 0.1 eV at room temperature for PuO 2 and NpO 2 , respectively, and compare our measurements with state-of-the-art calculations. V

The synthesis of pure δ-MoN with desired superconducting properties usually requires extreme conditions, such as high temperature and high pressure, which hinders its fundamental studies and applications. Herein, by using a chemical solution method, epitaxial δ-MoN thin films have been grown on c-cut Al(2)O(3) substrates at a temperature lower than 900 °C and an ambient pressure. The films are phase pure and show a T(c) of 13.0 K with a sharp transition. In addition, the films show a high critical field and excellent current carrying capabilities, which further prove the superior quality of these chemically prepared epitaxial thin films.

High quality epitaxial thin films of LaCoO 3 on SrTiO 3 have been prepared by spincoating of a metal/polymeric aqueous solution. The films (≈ 17 nm) are homogeneous and smooth over large areas. The characteristic low-spin (LS) state is replaced by a higher spin configuration of Co(III), due to strain-induced distortions of the CoO 6 octahedra, introducing a ferromagnetic interaction and negative magnetoresistance below T C = 85 K. This simple chemical method produces the high-quality films required for either fundamental studies or applications, similar to physical deposition techniques.