Search results for " defect"

First‐principles modelling of defects in advanced nuclear fuels

2007

In this paper we present and discuss the results of first first-principle modelling of point defects in nitride nuclear fuels. Calculations have been performed using the VASP computer code combined with supercells containing up to 250 atoms. The effective atomic charges, the electronic density redistribution, atomic displacements around U and N vacancies and their formation energies are discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

First-principles calculations of oxygen interstitials in corundum: a site symmetry approach

2017

The authors are indebted to R. Vila, A. Popov and A. Lushchik for stimulating discussions. This work was carried out within the framework of the EUROfusion Consortium and received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Support from Latvian National Research Program IMIS2 (2014–2017) is also appreciated. Calculations were carried out using both the Marconi supercomputer system at the Computational Simulation Centre and the Computer Center of St. Petersburg State University.

<title>Spatial correlation of latent image centers active in photostimulable luminescence of irradiated doped alkali halides</title>

2001

Changes in the photostimulated luminescence (PSL) spectrum of an electron irradiated KBr:Tl single crystal in relation to the A-luminescence spectrum upon direct activator ion excitation in the A-absorption band (AL) are found. Based on the view about the spatial correlation between F and activator hole centers, it is suggested that anion vacancy is an additional perturbing factor fot he activator (Tl+) excited (p-electron) state which is already subject to the dynamical Jahn-Teller effect. Dependences of the PSL efficiency on activator (In+) concentration in KBr:In samples irradiated by UV-light (6.30-6.45 eV), X-rays (30 keV or electrons (5.6 keV), are compared. The possible role of 6.45 …

Diffusion and reactions of interstitial oxygen species in amorphous SiO2: A review

2008

This article briefly summarizes the diffusion and reactions of interstitial oxygen species in amorphous SiO 2 (a-SiO 2 ). The most common form of interstitial oxygen species is oxygen molecule (O 2 ), which is sensitively detectable via its characteristic infrared photoluminescence (PL) at 1272 nm. The PL observation of interstitial 0 2 provides key data to verify various processes related to interstitial oxygen species: the dominant role of interstitial O 2 in long-range oxygen transport in a-SiO 2 ; formation of the Frenkel defect pair (Si-Si bond and interstitial oxygen atom, 0°) by dense electronic excitation; efficient photolysis of interstitial O 2 into O° with F 2 laser light (λ= 157…

Calculations of F centers in KNbO 3 ferroelectric crystals

1997

Semi-empirical method of the intermediate neglect of the differential overlap (INDO) combined with the supercell model is applied to the calculations of the F center optical properties in ferroelectric KNbO 3 perovskite crystals. It is shown that two electrons of the defect are weakly localized inside the O vacancy, unlike similar defects in ionic alkali halides, but are considerably spread over two nearest Nb atoms. For the orthorhombic phase stable at room temperatures three absorption bands are predicted to be at 2.72 eV, 3.04 eV and 3.11 eV, respectively. The first energy is close to the band at 2.7 eV observed in electron- irradiated crystals. In the high temperature, cubic phase only …

Magnetometry with Nitrogen-Vacancy Centers in Diamond

2016

This chapter covers magnetic sensing with nitrogen-vacancy (NV) defect centers in diamond. The NV center fundamentals are introduced and NV optically detected magnetic resonance techniques for dc and ac magnetic sensing are summarized. After reviewing some successful sensing applications, the advantages for using NV magnetometry, as well as some ongoing challenges, are enumerated.

Energy loss and fluence dependency of swift‐ion‐induced hardening in LiF

2005

The depth profiles of the hardening effects of LiF irradiated with swift Au, Pb, Bi, Kr, Ni and S ions of MeV-GeV energy have been studied as a function of ion penetration depth. For all projectiles, the hardness increases scaling with the range of ions and depending on ion fluence and energy loss. Heavy ions (Au, Pb, Bi), for which the energy loss noticeably exceeds the threshold of about 10 keV/nm for severe track core damage, cause uniform increase of hardness in the entire irradiated layer. For irradiations with lighter S, Ni, Kr ions, the hardening displays strong depth dependence. Ion-induced hardening is related to pinning of dislocations by defect aggregates (possibly small Li collo…

Microscopic theory of colloid formation in solids under irradiation

1996

Results of the first-principles study of diffusion-controlled aggregation of Frenkel defects-interstitial atoms-under irradiation of solids are presented. Conditions of the efficient radiation-induced aggregation of vacancies and interstitials are studied and the scenario of this process is presented.

A method for detecting vacancy diffusion in molecular dynamics

1992

Constructive Optimization of Vulcanization Installations in Order to Improve the Performance of Conveyor Belts

2019

Conveyor belts of special importance must have superior mechanical characteristics. The joining by vulcanization of the conveyor belts allows to obtain superior performances, but it has been found that at the vulcanizing joint of the conveyor belts, there is a &ldquo