Lead halide perovskite nanocrystals (NCs) are promising for applications in light emitting devices owing to a strong emission spectrum that is tunable throughout the visible region by altering halide composition. However, in mixed-halide perovskite systems photoinduced migration drives formation of halide-segregated domains, altering the emission spectrum. The mechanism by which this segregation occurs is currently the subject of intense investigation. Processes involving the perovskite surface are expected to be of enhanced prevalence in NCs due to their large surface area to volume ratio. In this work, we use transient absorption spectroscopy to probe the excited-state dynamics of NCs before and after halide segregation. Comparison of global fit spectra of the measured signals suggests the accumulation of iodide at the surface, resulting in a redshifted emission spectrum.

The transport and deposition of uranium under hydrothermal conditions in the Earth’s crust has been a subject of ongoing study but is yet to be completely understood. In addition, there is little known about the fate of nuclear waste, consisting of uranium from spent fuel and other radioactive materials, upon storage in repositories or in nuclear reactor facilities. Because the nuclear waste often comes in contact with aqueous fluids in storage environments, studies of uranyl complexation with chloride and other ligands in aqueous media, to high temperature and pressure conditions, are needed. The primary purpose of this study was to investigate the speciation of aqueous uranyl (VI) chloride complexes, in solutions having a 0.05 M uranyl concentration and [Cl] concentrations ranging from 0.2 M to 6 M, under hydrothermal conditions. The aqueous uranyl chloride complexes in the samples were studied using Raman spectroscopy and the hydrothermal diamond anvil cell (HDAC), at temperatures up to 500 °C and pressures up to ~ 0.5 GPa. The uranyl bond stretching band feature occurring in the ~810 to 870 cm-1 region was fitted using the Voigt peak shape to determine the speciation of the equilibrium uranyl chloride complexes present in the samples. As expected, the n integer value of the UO2Cln+2-n complex species increases with the increase in temperature and chloride concentration, generally trending toward charge neutrality at high temperatures.

Applying the Green's function based code FEFF to 5f derived features in actinide materials is potentially a very rewarding endeavor. However, there are some limitations that must be addressed. As part of the effort to quantify this process, FEFF has been applied to a few simplified 4f systems. The preliminary results of this investigation are discussed below.

We investigate whether first-principles calculations with an improved description of electronic correlations can explain the large magnetic moments and the strong magnetocrystalline anisotropy in the ferromagnetic compound UGa2. The correlations are treated within a static mean-field approximation DFT+U combining the density functional theory (DFT) with an onsite Hubbard interaction U. We find that DFT+U improves the agreement of the magnetic moments with the experiment compared to DFT but worsens the theoretical description of the magnetocrystalline anisotropy.

This paper reports a way to obtain BaPbO3-x and BaPb1/3Bi2/3O3-x perovskite-type compounds. The method is based on the initial preparation of Ba(COO)2⋅0.5H2O and Pb(COO)2⋅oxalates, and the subsequent calcination of the equimolar physical mixture of these oxalates until the desired compounds BaPbO3-x and BaPb1/3Bi2/3O3-x are formed. To obtain BaPb1/3Bi2/3O3-x, the oxide Bi2O3 is added to the mixture of oxalates and calcined together with them. The temperature for the formation of BaPbO3-x and BaPb1/3Bi2/3O3-x was estimated to be 850°C. These final compounds prepared by calcination were composed of a single phase and exhibited monoclinic crystal structure. The thermal decomposition of the Pb(COO)2 oxalate and the formation of BaPbO3-x and BaPb1/3Bi2/3O3-x were investigated by X-ray powder diffraction (XRPD) and differential thermal analysis (DTA).