In this paper we report positron lifetime results obtained under high-power steady-state and transient optical excitation. We present a model to analyse the results. The method has been applied to vacancy clusters in natural diamond, for which we self-consistently analyse optoelectronic constants such as optical absorption cross section and hole recombination cross section. The temperature depe...

A ngular distri buti ons of the positron annihil ati on quanta were measured for pure and hydrogenated palladi um samples deformed by unia xi al tension up to di ̃erent deformation degrees. T he relative di ̃erence curves, and the values of the R parameter characteri zing the dimensions of defects trapping the positrons, w ere determined. I t w as found that for relative elongation s ranging from...

We study from first principles the magnetism in graphene induced by single carbon atom defects. For two types of defects considered in our study, the hydrogen chemisorption defect and the vacancy defect, the itinerant magnetism due to the defect-induced extended states has been observed. Calculated magnetic moments are equal to 1 B per hydrogen chemisorption defect and 1.12–1.53 B per vacancy d...

We discuss how electronic-structure calculations can be used to identify the dominant point defects that control the growth and dissolution of the oxide barrier layer formed if a metal comes into contact with a corrosive environment. Using the example of the Zn/ZnO/H(2)O interface we develop and apply a theoretical approach that is firmly based on ab initio computed defect formation energies an...

Determining vacancy in complex crystals or nanostructures represents an outstanding crystallographic problem that has a large impact on technology, especially for semiconductors, where vacancies introduce defect levels and modify the electronic structure. However, vacancy is hard to locate and its structure is difficult to probe experimentally. Reported here are atomic vacancies in the InAs/GaS...

First principles total energy calculations were performed in order to characterize O vacancy defects in Ta O . A simplified 2 5 version of the crystalline orthorhombic phase of Ta O was used in this study. Results indicate that O vacancies in Ta O 2 5 2 5 can be broadly classified based on their location in the lattice. One type of vacancy (occupying the ‘in-plane’ sites) displays deep or mid g...

First principles total energy calculations were performed to characterize oxygen vacancy defects in tantalum pentoxide (Ta2O5). A simplified version of the crystalline orthorhombic phase of Ta2O5 was used in this study. Results indicate that O vacancies in Ta2O5 can be broadly classified based on their location in the lattice. One type of vacancy that occupies the ‘‘in-plane’’ sites displays de...

We examine the effects of vacancy defects on thermal conductivity in bulk crystalline silicon (c-Si) using nonequilibrium molecular dynamics simulations. While most vacancies are thought to remain in the form of clusters in bulk c-Si, recent theoretical studies have predicted that small vacancy clusters energetically prefer to be fourfold coordinated by nullifying dangling bonds. Hence, in this...

Zirconium alloys are subjected to a fast neutron flux in nuclear reactors, inducing the creation of large number point defects, both vacancy and self-interstitial. These defects then diffuse can be trapped by their different sinks or cluster form larger such as interstitial clusters. In this work, trapping capability small-vacancy clusters (two/three vacancies, V2/V3) α-Zr doped with alloying e...

Showed that the calculated activation energy for • AlH3 vacancy diffusion in NaAlH4 is 85 kJ/mol H2, suggesting that it is the rate-limiting step in hydrogen release kinetics from Ti-doped samples. Obtained the activation energies for surface• controlled vacancy creation in pure undoped NaAlH4, showed that vacancy creation limits the dehydrogenation kinetics for particle sizes above ~0.1 μm. Id...