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Interstitial Atoms (interstitial + atom)

Distribution by Scientific Domains

Physics and Astronomy	40%
Chemistry	40%

Selected Abstracts

The effect of interstitial hydrogen on the electronic structure of the B2 FeAl alloy

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007
Estela A. González
Abstract The electronic structure and bonding in a B2 Fe,Al alloy with and without hydrogen as an interstitial atom were studied within the framework of the density functional theory and the findings compared with previous results in Fe an Al. The hydrogen absorption turns out to be a favorable process. The hydrogen was found near an Al octahedral site, the Al,H distance being shorter than that of Fe,H. The density of states (DOS) curves show several peaks below the d metal band which is made up mostly of hydrogen based states (>50% H1s) while the metal contribution includes mainly s- and p-orbitals. An electron transfer of nearby 0.14 e, comes from the metal to the H. The overlap population values reveal metal,metal bond breaking, the intermetallic bond being the most affected. The H bond mainly with the Al atoms and the reported Fe,H overlap population is much lower than that corresponding to FePd alloys and BCC Fe. The changes in the overlap population show the Fe,Al bond is weakening nearly 53% after H absorption, while the Fe,Fe bond is only weakened 23%. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electron beam,specimen interactions and their effect on high-angle annular dark-field imaging of dopant atoms within a crystal

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2010
B. G. Mendis
A Bloch wave model based on perturbation theory is used to analyse high-angle annular dark-field (HAADF) imaging of a substitutional and interstitial W atom in [111]-oriented body-centred-cubic Fe. For the substitutional atom the 1s Bloch state is scattered to high angles thereby producing HAADF dopant atom contrast. Intraband scattering of the 1s state is the strongest individual Bloch wave transition but collective interband scattering of the non-1s states to the 1s state leads to variations in the high-angle scattering with depth of the dopant atom. The non-1s states are Coulomb attracted towards the W atom thereby giving rise to an `atom focusing' effect similar to channelling. For the interstitial atom, which in the [111] orientation does not overlap with an atom column of the host lattice, high-angle scattering and Coulomb attraction takes place through the non-1s states. Scattering of the 1s state is, however, negligible. [source]

Recent Progress in Exploring Magnetocaloric Materials

ADVANCED MATERIALS, Issue 45 2009
B. G. Shen
Abstract The magnetic refrigeration technique based on the magnetocaloric effect (MCE) has attracted increasing interest because of its high efficiency and environment friendliness. In this article, our recent progress in exploring effective MCE materials is reviewed with emphasis on the MCE in the LaFe13,xSixbased alloys discovered by us. These alloys show large entropy changes over a wide temperature range near room temperature. The effects of magnetic rare-earth doping, interstitial atoms and high pressure on the MCE have been systematically studied. Special issues, such as appropriate approaches to determining the MCE associated with the first-order magnetic transition, the depression of magnetic and thermal hysteresis, and the key factors determining the magnetic exchange in alloys of this kind, are discussed. The applicability of giant MCE materials to magnetic refrigeration near ambient temperature is evaluated. A brief review of other materials with significant MCE is also presented. [source]

Radiation-induced structural transformations in a silicon layer of SOI

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2007
K. D. Shcherbachev
Abstract The differences in the secondary processes proceeding in the silicon layer of SOI and reference bulk silicon wafers are revealed by using High-Resolution X-ray diffraction and Rutherford Backscattering spectroscopy methods. The damage depth profiles in the implanted layers described by both strain and static Debye,Waller factor profiles, were reconstructed from the diffraction patterns using an autofitting procedure, based on a genetic algorithm. The contribution of diffuse scattering was excluded using the triple-crystal diffractometry technique. The defect density profiles were obtained from the RBS/Channelling measurements, which were carried out using 4He+ beam at 2.0 MeV. The DICADA code, based on the theoretical description of dechanneling was used to interpret the RBS/C data. Accumulation kinetics, spatial distribution, and concentration of radiation-induced defects in the topmost silicon layer of SOI and a bulk silicon were shown to be essentially different. The influence of the fields was shown to lead to the loss of crystallinity of the thin surface layer of silicon in SOI due to accumulation of vacancy-type defects and increase of concentration of interstitial atoms near the internal interphase boundary "Si,SiO2". (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Bond analyses of borates from the Inorganic Crystal Structure Database

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2006
Daqiu Yu
Various fundamental building blocks (FBBs) are observed in the crystallographic structures of oxoborates available in the Inorganic Crystal Structure Database, Version 1.3.3 (2004); the occurrence of borate groups with low complexity is dominant. Bond-valence parameters d0 of B,O bonds in 758 oxoborates with various FBBs have been calculated using the bond-valence sum model. Some discrepancies in the d0 values obviously occur if the detailed configurations of FBBs in borate crystals are considered; d0 is sensitive to the chemical bonding structure of B atoms in the crystallographic framework. Moreover, d0 values are affected by the existence of interstitial atoms and the substitution of other anionic groups. In addition, the d0 parameters for B,N, B,S, B,P and B,F bonds are also calculated statistically. Some suitable d0 data for various borate FBBs are recommended according to their particular configurations, especially for those with low complexity. On the basis of the proposed linear relationship between calculated nonlinear optical (NLO) coefficients of borates and the current d0 values for various FBBs, it is found that the d0 values may be regarded as a useful parameter for pre-investigating the NLO properties of borates, leading to an efficient structural evaluation and design of novel borates. [source]