Static and dynamic evolution of CO adsorption onγ-U(100)surface with different levels of Mo doping using DFT and AIMD calculations

Alloys of uranium and molybdenum are considered as the future of nuclear fuel and defense materials.However,surface corrosion is a fundamental problem in practical applications and storage.In this study,the static and dynamic evolution of carbon monoxide(CO)adsorption and dissociation onγ-U(100)surface with different Mo doping levels was investigated based on density functional theory and ab initio molecular dynamics.During the static calculation phase,parameters,such as adsorption energy,configuration,and Bader charge,were evaluated at all adsorption sites.Furthermore,the time-dependent behavior of CO molecule adsorption were investigated at the most favorable sites.The minimum energy paths for CO molecu-lar dissociation and atom migration were investigated using the transition state search method.The results demonstrated that the CO on the uranium surface mainly manifests as chemical adsorption before dissociation of the CO molecule.The CO molecule exhibited a tendency to rotate and tilt upright adsorption.However,it is difficult for CO adsorption on the surface in one of the configurations with CO molecule in vertical direction but oxygen(O)is closer to the surface.Bader charge illustrates that the charge transfers from slab atoms to the 2π*antibonding orbital of CO molecule and particularly occurs in carbon(C)atoms.The time is less than 100 fs for the adsorptions that forms embryos with tilt upright in dynamics evolution.The density of states elucidates that the overlapping hybridization of C and O 2p orbitals is mainly formed via the d orbitals of uranium and molybdenum(Mo)atoms in the dissociation and re-adsorption of CO molecule.In conclusion,Mo doping of the surface can decelerate the adsorption and dissociation of CO molecules.A Mo-doped surface,created through ion injection,enhanced the resistance to uranium-induced surface corrosion.

OKMC simulation of vacancy-enhanced Cu solute segregation affected by temperature/irradiation in the Fe–Cu system

The effects of annealing and irradiation on the evolution of Cu clusters in a-Fe are investigated using object kinetic Monte Carlo simulations.In our model,vacancies act as carriers for chemical species via thermally activated diffusion jumps,thus playing an important role in solute diffusion.At the end of the Cu cluster evolution,the simulations of the average radius and number density of the clusters are consistent with the experimental data,which indicates that the proposed simulation model is applicable and effective.For the simulation of the annealing process,it is found that the evolution of the cluster size roughly follows the 1/2 time power law with the increase in radius during the growth phase and the 1/3 time power law during the coarsening phase.In addition,the main difference between neutron and ion irradiation is the growth and evolution process of the copper-vacancy clusters.The aggregation of vacancy clusters under ion irradiation suppresses the migration and coarsening of the clusters,which ultimately leads to a smaller average radius of the copper clusters.Our proposed simulation model can supplement experimental analyses and provide a detailed evolution mechanism of vacancy-enhanced precipitation,thereby providing a foundation for other elemental precipitation research.

Unique redox properties in defective CeO_(2-x) nanocrystallines synthesized by laser melting

Defects in cerium oxide, especially oxygen va- cancies, play an essential role in its versatile applications and are efficiently preserved at ambient conditions in a non- equilibrium process. Herein, defective CeO2x with hetero- geneous structure was synthesized by high-energy laser melt- ing, where a large amount of oxygen vacancies and Ce3~ could be introduced, leading to improved visible light absorption, narrowed bandgap and room temperature ferromagnetism. Moreover, this laser melted CeO2x exhibits significantly en- hanced low-temperature oxidation behaviors than the coun- terpart prepared by normal hydrogen-reduction. This unique redox performance could be attributed to the intragranular diffusion at the boundaries of assembled nanocrystallites. This method paves a new way for introducing unique multi-func- tions in oxide ceramics.

Theoretical analysis on GaAs sub-cell doping concentration for triple-junction solar cells irradiated by proton based on TCAD simulation

The degradation on the GaInP/GaAs/Ge triple-junction solar cells was irradiated by proton, and the solar cells with various GaAs sub-cell doping concentrations are modeled by the technology computer aided design(TCAD) simulation. The degradation results of related electrical parameters and external quantum efficiency(EQE) are studied. The degradation mechanism irradiated by proton is discussed. The short-circuit current, maximum power and conversion efficiency decrease with the increasing of GaAs sub-cell doping concentration. When the base doping concentration of GaAs sub-cell is 1×1016cm-3, the degradation of short-circuit current is less than that of other base doping concentrations. Furthermore, under proton irradiation, with the increase of doping concentration of GaAs sub-cell, the open-circuit voltage first increases and then decreases. Meanwhile, when the base doping concentration of GaAs sub-cell is 2×10^(17)cm^(-3), the degradation of open-circuit voltage is less than that of other base doping concentrations. The research will provide the basic theories and device simulation method for GaInP/GaAs/Ge triple-junction solar cells radiation damage evaluation study and radiation hardening, and can provide guidance for the production of triple-junction solar cells in orbit.