The features of deformation-stimulated RbI luminescence

This paper studies deformation-stimulated features of radiative relaxation of self-trapped excitons and recombination assembly of exciton-like luminescence in RbI crystal. Methods of research were luminescence and thermal activation spectroscopy. The identity of the mechanism of manifestation of the X-ray luminescence, tunnel luminescence and thermally stimulated luminescence spectra were found in the elastically deformed RbI crystal, interpreted by the luminescence of self-trapped exciton, tunnel recharge of F′, VK -pairs and thermally stimulated recombination of e−, VK -centres, respectively.The temperatures of the maximum destruction peaks of thermally stimulated luminescence, their spectral composition and activation energies were determined experimentally, on the basis of which the mechanisms of recombination assembly of exciton-like luminescences in a RbI crystal were interpreted. Uniaxial elastic deformation leads to the effective formation of point radiation defects ( F′, HA, VK -centers) in comparison with an unbroken lattice, where the predominant mechanism is the association of interstitial atoms ( H -centres) with the formation of I3−-centres.

Strain Effects on the Diffusion Properties of Near-Surface Self-Interstitial Atoms and Adatoms in Tungsten

Tungsten (W) is a candidate for the plasma-facing components and divertor in future fusion applications. The material will be subject to a large particle influx (mainly helium and hydrogenic species) that will form bubbles. As bubbles grow, they compress the material, adding to thermal stresses, and eject self-interstitial atoms (SIAs—isolated or in clusters) to release internal pressure. These SIAs diffuse towards the surface in large stress/strain fields and on the surface are thought to act as precursors for nanotendril formation (also known as fuzz) that develops on the material surface modifying its morphology. In this work we analyze the effect of strain on the diffusion properties of both SIAs and adatoms. Relying on atomistic simulations, we compute the average time that a SIA created in the center of a tungsten slab takes to reach a (110) surface for different strains and temperatures. This time relates to the SIA diffusivity and allows to compute the activation energy and dipole tensor including surface effects. We observe a large strain effect that significantly modifies the propensity for SIAs to reach the surface and, hence, to cluster to form dislocation loops in the bulk crystal. Strain also alters the diffusivity of the adatom although to a lesser extent. Finally, we report on the resulting surface roughness evolution and its dependence on strain.

Molecular Dynamics Study of Interaction of Carbon, Nitrogen, and Oxygen Impurity Atoms with Self-Interstitial Atoms in Nickel, Silver and Aluminum

The interaction of impurity atoms of carbon, nitrogen, and oxygen with self-interstitial atoms in FCC metals like nickel, silver, and aluminum is studied using the molecular dynamics method. It is found that the self-interstitial atom migration in the crystal lattice follows two mechanisms: dumbbell and crowdion. In this case, the first mechanism that includes one interatomic distance displacement and the rotation of the <001> dumbbell is characterized by broken paths of atomic migration. The second mechanism is described by straight paths along the close-packed directions <011> in the crystal. The binding energies between impurity atoms and selfinterstitial atoms in Ni, Ag, and Al are calculated in the paper. It is shown that impurity atoms are effective “traps” for interstitial atoms that migrate relatively quickly in a crystal. During the interaction of an interstitial and an impurity atom, the interstitial atom forms a dumbbell configuration with an axis along the <001> direction, and the impurity atom is located in the nearest octahedral pore. It is found that the mobility of interstitial atoms is significantly reduced due to the presence of impurities in the metal. The introduction of 10 % impurity atoms leads to a severalfold increase in the migration energy of interstitial atoms. At the same time, the contribution of the crowdion mechanism is noticeably reduced while the dumbbell mechanism contribution is increased.