Using molecular dynamics simulations of UO2-a type II superionic conductor-we identify a well-defined onset of dynamic disorder (Tα), which is remarkably correlated to a nontrivial advance of dynamical heterogeneity (DH). Quantified by the correlations in the dynamic propensity and van Hove self-correlation function, the DH is shown to grow with increasing temperature from Tα, peak at an intermediate temperature between Tα and Tλ-the superionic transition temperature-and then recede. Surprisingly, the DH attributes are not uniform across the temperatures-our investigation shows a low temperature (αT) stage DH, which is characterized by weak correlations and a plateaulike period in the correlations of the propensity, and a high temperature (λT) stage DH with strong correlations that are analogous to those in typical supercooled liquids. Our work, which has rigorously identified the onset of superionicity, gives a different direction for interpreting scattering experiments on the basis of statistical, correlated dynamics.
Molecular dynamics (MD) simulations are carried out to understand the mechanisms of damage production and recovery near grain boundaries in β-SiC under neutron irradiation. Our investigations show that the damage generated by radiation is reduced by the presence of a ∑9{122}[110] tilt grain boundary. Directional displacements which are averaged over an isoconfigurational ensemble are used to characterize the statistical nature of atomic mobility near the grain boundary.
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