scholarly journals Polaronic deformation at theFe2+/3+impurity site inFe:LiNbO3crystals

2015 ◽  
Vol 91 (9) ◽  
Author(s):  
A. Sanson ◽  
A. Zaltron ◽  
N. Argiolas ◽  
C. Sada ◽  
M. Bazzan ◽  
...  
Keyword(s):  
Impurity Site

Environment Sensitive Embedding Energies of Impurities, and Grain Boundary Relaxation in Iron

1991 ◽  
Vol 238 ◽  
Author(s):  
Genrich L. Krasko
Keyword(s):  
Charge Density ◽  
First Principles ◽  
Electron Charge ◽  
Deformation Wave ◽  
Electron Charge Density ◽  
Impurity Site ◽  
Embedded Atom ◽  
Bcc Iron ◽  
Boundary Relaxation ◽  
Low Solubility

ABSTRACTImpurities, such as H, P, S, B, etc, have a very low solubility in iron, and therefore prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the iron GB, the LMTO calculations were performed on a simple 8-atom supercel 1 emulating a typical (capped trigonal prism) GB environment. The so-called “environment-sensitive embedding energies” were calculated for H, B, C, N, O, Al, Si, P, and S, as a function of the electron charge density due to the host atoms at the impurity site. It was shown that, at the electron charge density typical of a GB, B and C have the lowest energy among the analyzed impurities, and thus would compete with them for the site on the GB, tending to push the other impurities off the GB. The above energies were then used in a modified Finnis-Sinclair embedded atom approach for calculating the equilibrium interplanar distances in the vicinity of a (111) σ3 tilt GB plane, both for the clean GB and that with an impurity. These distances were found to be oscillating, returning to the equilibrium spacing between (111) planes in bulk BCC iron by the 10th-12th plane off the GB plane. H, B, C, N and O actually dampen the deformation wave (making the oscillation amplitudes less than in the clean GB), while, Al, Si, P and S result in an increase of the oscillations. The effect of B, C, N and O may be interpreted as cohesion enhancement; this conclusion supports our earlier first-principles results [1] on B and C.

Spontaneous Tunnel Transitions Induced by Redistribution of Trapped Electrons over Impurity Centers

1983 ◽  
Vol 38 (9) ◽  
pp. 959-962
Author(s):  
A. A. Berezin
Keyword(s):  
Excited State ◽  
Charge State ◽  
Ground State ◽  
Low Energy ◽  
Energy Photon ◽  
Impurity Site ◽  
The Third ◽  
Tunnel Transition ◽  
Extra Electron ◽  
Impurity Centers

Abstract A system of polyvalent impurity centers in a semiconductor (i.e. Au-centers in Si) is con-sidered. The ground state of the impurity pair Au-(a) + Au° (b), where an extra electron is localized on the site a, may be turned into an excited state due to a change of the charge state of a third nearby impurity site. This happens because of different shifts of the Au--level at sites a and b due to their different distances from the third center. As a result, the original pair is able to reach a new ground state Au° (a) + Au- (b) through a slow spontaneous tunnel transition. The probability of this transition, when it is accompanied by an emission of a low energy photon, is calculated explicitly.

Paramagnetic impurities in an itinerant antiferromagnet. Theory

1969 ◽  
Vol 47 (5) ◽  
pp. 477-487 ◽  
Author(s):  
S. N. Behera ◽  
K. S. Viswanathan
Keyword(s):  
Density Of States ◽  
Energy Gap ◽  
Impurity Site ◽  
Atom Ratio ◽  
Hartree Fock ◽  
Paramagnetic Impurities ◽  
Spin Dependent Scattering ◽  
Experimental Findings ◽  
Gap Parameter ◽  
Theory And Experiment

The effects of 3-d paramagnetic impurities in an itinerant antiferromagnetic metal are investigated using the Wolff–Clogston model. The changes in the Néel temperature TN, the energy-gap parameter, and the density of states are evaluated in the Hartree–Fock approximation and in the lowest order in the impurity concentration. The results on the changes in TN are compared with the experimental findings on V, Mn, Fe, Co, Ni, Mo, and W impurities in chromium. The agreement between theory and experiment suggests that the changes in TN are essentially due to three mechanisms: (a) the effect due to changes in the electron–atom ratio, (b) the spin-dependent scattering due to paramagnetic impurities, and (c) the changes in the intra-atomic coulomb potential at the impurity site. In the case of Mo and W, the last effect explains the observed decrease in TN in Cr.

OPTICAL PROPERTIES OF UNDOPED AND Ni-DOPED SbSBr AND BiSBr SINGLE CRYSTALS

1995 ◽  
Vol 09 (03n04) ◽  
pp. 229-235
Author(s):  
MOON-SEOG JIN ◽  
HO-JUN SONG ◽  
YONG-GEUN KIM ◽  
HYUNG-GON KIM ◽  
JEONG-DAE KOH ◽  
...  
Keyword(s):  
Single Crystals ◽  
Energy Gap ◽  
Energy Levels ◽  
Bridgman Technique ◽  
Optical Energy Gap ◽  
Impurity Site ◽  
First Order ◽  
Electron Transitions ◽  
First Order Phase Transition ◽  
First Order Phase

SbSBr, BiSBr, SbSBr:Ni, and BiSBr:Ni single crystals were grown by the Bridgman technique. The grown single crystals crystallized in an orthorhombic structure and have an indirect band structure. The temperature dependence of their optical energy gap shows an anomalous property at the first order phase transition temperature and at the second order one. Nickel doped as an impurity site at the T d symmetry point in the host single crystals as Ni 2+ ion. The impurity optical absorption peaks appeared by the electron transitions between the energy levels of these ions.

Raman scattering from impurities in semiconductors. I. General result

1978 ◽  
Vol 56 (5) ◽  
pp. 550-559 ◽  
Author(s):  
Robert Barrie ◽  
I. W. Sharpe
Keyword(s):  
Raman Scattering ◽  
General Result ◽  
Adiabatic Approximation ◽  
Phonon Coupling ◽  
Mathematical Technique ◽  
Impurity Site ◽  
Absorption And Emission ◽  
Systematic Fashion ◽  
Impurities In Semiconductors ◽  
Electron Phonon Coupling

A mathematical technique previously used for studying absorption and emission from impurity centres in semiconductors is applied to Raman scattering from such centres. The usual adiabatic approximation is not made. The method makes use of the fact that at most one electron can be bound at the impurity site and reduces the problem in a systematic fashion to the evaluation of traces over only phonon states. These traces are evaluated for a particular type of electron–phonon coupling.

IMPURITY EFFECTS ON THE ENTANGLEMENT OF SPIN-ONE HEISENBERG MODEL

2008 ◽  
Vol 22 (20) ◽  
pp. 1923-1930 ◽  
Author(s):  
MING-LIANG HU
Keyword(s):  
Heisenberg Model ◽  
Thermal Fluctuations ◽  
Threshold Temperature ◽  
Heisenberg Chain ◽  
Impurity Effects ◽  
Impurity Site

The entanglement characteristics of the three-qutrit spin-one Heisenberg chain in the presence of one impurity site is investigated by using the concept of negativity. The results show that the existence of impurity can lead to an enhancement of both bipartite and pairwise entanglement for certain ranges of the impurity parameter, and the amount of entanglement can be controlled and tuned by varying the impurity parameter J1. The results also show that the thermal fluctuations always suppress the entanglement and as a result there exists a threshold temperature Tth after which the entanglement vanishes. Tth increases as J1 increases except the case for that of the pairwise negativity [Formula: see text] which measures entanglement between the two norm spins in the chain.

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