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Impurity Atoms (impurity + atom)

Distribution by Scientific Domains

Physics and Astronomy	40%
Chemistry	40%

Selected Abstracts

Structure,Property,Function Relationships in Nanoscale Oxide Sensors: A Case Study Based on Zinc Oxide,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007
S. Polarz
Abstract Chemical sensing on oxide sensors is a complex phenomenon involving catalytic activity as well as electronic properties. Thus, the properties of oxide sensors are highly sensitive towards structural changes. Effects like surface area, grain size, and, in addition, the occurrence of defects give separate contributions to the current. Structure,property,function relationships can be elucidated using a combination of state-of-the-art analytical techniques. It is shown, that impurity atoms in the oxide lattice influence the performance of ZnO sensors more strongly than the other factors. [source]

The magnetic moments and their long-range ordering for Fe atoms in a wide variety of metallic environments

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2010
A. Ayuela
Abstract The magnitudes of Fe magnetic moments, together with their long-range ordering when appropriate, are compared and contrasted in a variety of metallic environments. Thus, Fe, in its stable body-centered-cubic (bcc) phase under ambient conditions, is considered under pressures p, which can yield different crystal structures at high p, including fcc. The modification of the ferromagnetism in bcc Fe is surveyed as one passes through a bc-tetragonal lattice to the fcc form. In the latter, evidence is presented, both from theory and experiment, that the ordering is antiferromagnetic in character. Then, binary metallic alloys with Fe atoms as the majority component are considered, Fe,Co and Fe,Ga being focal points in both ordered and disordered materials. Finally, some discussion is given, involving again both experiment and theory, of the possible spin polarization of neighboring Cs atoms when Fe impurity atoms are inserted into the low conduction electron density characterizing this heavy alkali metal under ambient conditions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Electronic structure and magnetic properties of Fe3C with 3d and 4d impurities

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
I. R. Shein
Abstract We study the electronic structure, formation energies, and magnetic properties of cementite Fe3C doped by 3d and 4d transition metals (TM) by means of first-principles calculations. All TM elements demonstrate a preference for the substitution of the general iron position in Fe3C. We predict that early elements (Sc, Ti, V, Cr, Zr, and Nb) stabilize the cementite, while the end elements (Ni, Cu, Pd, and Ag) in the TM series sharply destabilize it. The magnetic properties of impurity atoms are found to depend strongly on their atomic numbers and the trends to ferromagnetic or antiferromagnetic coupling of impurities with Fe atoms in Fe3C coincide with the magnetic behavior of these impurities in Fe. The physical reason is a similar location of the Fermi level in the pseudogap of spin-down and almost filled spin-up Fed states in both Fe3C and Fe. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A theory of nonlinear susceptibility in polaritonic band-gap materials doped with multi-level atoms

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005
D. Mukherji
Abstract We have studied the nonlinear susceptibility in dispersive polaritonic band-gap (DPBG) materials in the presence of five-level impurity atoms. Initially, the atom is prepared in a coherent superposition of two levels |b, and |c,. The levels |b, and |c, are coupled to the upper level |a, with a coherent laser field. The nonlinear susceptibility has been calculated corresponding to transitions |a, , |c, and |a, , |b, using the equation of motion for the density matrix. The atomic system is interacting with the polariton reservoir. The effect of atom-polariton reservoir coupling on the imaginary part of the nonlinear susceptibility has been studied when the resonance energy lies in lower band of the polariton spectrum. It is found that by shifting the resonance energy away from the band edge, the system goes to the probe gain state. It is also found that by changing the intensity of the coherent laser field, the system switches from gain to loss state and vice-versa. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Resonant X-ray diffraction: `forbidden' Bragg reflections induced by thermal vibrations and point defects

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2000
V. E. Dmitrienko
In general, the local atomic environment becomes less symmetric owing to point defects and thermal vibrations of atoms in crystals. It is shown that, as a result of this phenomenon, an additional anisotropy of the resonant scattering factors can occur and the forbidden Bragg reflections can be excited near absorption edges. Examples of crystals are presented (Ge, K2CrO4, C-15 type) where such thermal-motion-induced (TMI) and point-defect-induced (PDI) reflections can be observed. The tensor structure factors of both types of reflection are computed. Owing to their resonant character, the PDI reflections allow both impurity atoms and host atoms of different types to be studied separately. The considered phenomena can provide a very sensitive method to study point defects because only the atoms distorted by defects produce contributions to the PDI reflections. [source]