Band-Edge Engineering To Eliminate Radiation-Induced Defect States in Perovskite Scintillators.

Under radiative environments such as extended hard X- or γ-rays, degradation of scintillation performance is often due to irradiation-induced defects. To overcome the effect of deleterious defects, novel design mitigation strategies are needed to identify and design more resilient materials. The potential for band-edge engineering to eliminate the effect of radiation-induced defect states in rare-earth-doped perovskite scintillators is explored, taking Ce-doped LuAlO as a model material system, using density functional theory (DFT)-based DFT + and hybrid Heyd-Scuseria-Ernzerhof (HSE) calculations.

Determination of Krypton Diffusion Coefficients in Uranium Dioxide Using Atomic Scale Calculations.

We present a study of the diffusion of krypton in UO using atomic scale calculations combined with diffusion models adapted to the system studied. The migration barriers of the elementary mechanisms for interstitial or vacancy assisted migration are calculated in the DFT+U framework using the nudged elastic band method. The attempt frequencies are obtained from the phonon modes of the defect at the initial and saddle points using empirical potential methods.

Hydrogen bond disruption in DNA base pairs from (14)C transmutation.

Recent ab initio molecular dynamics simulations have shown that radioactive carbon does not normally fragment DNA bases when it decays. Motivated by this finding, density functional theory and Bader analysis have been used to quantify the effect of C → N transmutation on hydrogen bonding in DNA base pairs. We find that (14)C decay has the potential to significantly alter hydrogen bonds in a variety of ways including direct proton shuttling (thymine and cytosine), thermally activated proton shuttling (guanine), and hydrogen bond breaking (cytosine).

Mixing and non-stoichiometry in Fe-Ni-Cr-Zn-O spinel compounds: density functional theory calculations.

Density functional theory (DFT) calculations have been performed on A(2+)B2(3+)O4(2-) (where A(2+) = Fe, Ni or Zn, and B(3+) = Fe or Cr) spinel oxides in order to determine some of their thermodynamic properties. Mixing energies were calculated for Fe3O4-NiFe2O4, Fe3O4-ZnFe2O4, Fe3O4-FeCr2O4, NiFe2O4-ZnFe2O4, NiFe2O4-NiCr2O4, FeCr2O4-NiCr2O4, FeCr2O4-ZnCr2O4 and ZnCr2O4-ZnFe2O4 pseudo-binaries based on special quasi random (SQS) structures to account for cationic disorder. The results generally agree with available experimental data and the rule that two normal or two inverse spinel compounds easily form solid solutions, while inverse-normal spinel mixtures exhibit positive deviation from solid solution behavior (i.

Energetics of cation mixing in urania-ceria solid solutions with stoichiometric oxygen concentrations.

Cation mixing energetics in urania-ceria solid solutions with stoichiometric oxygen concentrations (U(1-y)Ce(y)O(2)) have been measured by high-temperature oxide-melt drop-solution calorimetry. Measurements have been performed on eight samples with compositions spanning y = 0.119 to y = 0.

Radiation-induced amorphization resistance and radiation tolerance in structurally related oxides.

Ceramics destined for use in hostile environments such as nuclear reactors or waste immobilization must be highly durable and especially resistant to radiation damage effects. In particular, they must not be prone to amorphization or swelling. Few ceramics meet these criteria and much work has been devoted in recent years to identifying radiation-tolerant ceramics and the characteristics that promote radiation tolerance.