Study on anisotropies and momentum densities in AlN, GaN and InN by positron annihilation

2016 ◽  
Vol 12 (3) ◽  
pp. 4356-4367
Author(s):  
N. Amrane ◽  
M. Benkraouda ◽  
N. Qamhieh ◽  
Saleh T. Mahmoud
Keyword(s):  
Particle Model ◽  
Computational Technique ◽  
Annihilation Radiation ◽  
Charge Densities ◽  
Empirical Pseudopotential Method ◽  
Electron Positron ◽  
Independent Particle ◽  
Independent Particle Model ◽  
Bond Center ◽  
Initial Results

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalized positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8-N. Initial results show a clear asymmetrical positron charge distribution relative to the bond center. It is observed that the positron density is maximum in the open interstices and is excluded not only, from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001,110) planes. The results are used to analyze the positron effects in AlN, GaN and InN compounds. Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the twodimensional angular correlation of annihilation radiation (2D-ACAR).

STUDY ON MOMENTUM DENSITY IN SEMICONDUCTOR ALLOYS GeC and SnC BY POSITRON ANNIHILATION

2010 ◽  
Vol 24 (18) ◽  
pp. 3607-3618
Author(s):  
N. AMRANE
Keyword(s):  
Momentum Density ◽  
Particle Model ◽  
Computational Technique ◽  
Annihilation Radiation ◽  
Charge Densities ◽  
Electron Positron ◽  
Independent Particle ◽  
Independent Particle Model ◽  
Bond Center ◽  
Initial Results

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalized positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8-N . Initial results show a clear asymmetrical positron charge distribution relative to the bond center. It is observed that the positron density is maximum in the open interstices and is excluded not only from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001, 110) planes. The results are used to analyze the positron effects in GeC and SnC . Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the two-dimensional angular correlation of annihilation radiation (2D-ACAR).

POSITRON STATES IN Si1-xGex ALLOYS: DEVIATION FROM VEGARD'S LAW

2002 ◽  
Vol 16 (08) ◽  
pp. 275-283 ◽  
Author(s):  
N. BOUARISSA
Keyword(s):  
Positron Lifetime ◽  
Alloy Composition ◽  
Particle Model ◽  
Annihilation Rate ◽  
Positron States ◽  
Electron Positron ◽  
Independent Particle ◽  
Vegard’S Law ◽  
Independent Particle Model ◽  
Positron Lifetime Measurement

Electron-positron momentum densities along different crystallographic directions and positron bulk lifetime in Si 1-x Ge x alloys have been investigated within the pseudopotential formalism employing the independent particle model. Special attention has been given to the effect of the deviation of the alloy lattice parameters from Vegard's rule on the studied quantities. It is found that using Vegard's law leads to an underestimation of the total positron annihilation rate indicating therefore an overestimation of the positron bulk lifetime. This result could not be checked using the Siethoff relation (H. Siethoff, Phys. Stat. Sol.B205, R3 (1998)). Moreover, this relation predicts a monotonic dependence of the positron bulk lifetime on the alloy composition which disagrees with the positron lifetime measurement.

Potential barrier effect and discrete structure o between 40 and 120 Å in the Rb I absorption spectrum

1975 ◽  
Vol 344 (1637) ◽  
pp. 303-309 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Absorption Maximum ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Particle Model ◽  
Discrete Structure ◽  
Model Calculations ◽  
Hartree Fock ◽  
Independent Particle ◽  
Independent Particle Model

Investigation of the Rb I absorption spectrum between 40 and 120 Å has revealed a broad absorption maximum in the 3d photoionization continuum, as well as discrete features associated with the excitation of a 3d-subshell electron. The discrete structure is identified, Hartree-Fock calculations of the transition energies are given and the absorption maximum is discussed in relation to similar spectra and to recent random phase approximation with exchange (r.p.a.e.) and independent particle model calculations.

scholarly journals Electron capture into few-electron heavy ions: Independent particle model

2007 ◽  
Vol 46 (1) ◽  
pp. 27-36 ◽  
Author(s):  
A. Surzhykov ◽  
U. D. Jentschura ◽  
T. Stöhlker ◽  
S. Fritzsche
Keyword(s):  
Electron Capture ◽  
Heavy Ions ◽  
Particle Model ◽  
Independent Particle ◽  
Independent Particle Model

The history, development, and future prospects for (e,2e) spectroscopy

1996 ◽  
Vol 74 (11-12) ◽  
pp. 703-712 ◽  
Author(s):  
Ian E. McCarthy
Keyword(s):  
Nuclear Physics ◽  
Experimental Result ◽  
Particle Model ◽  
Sensitive Information ◽  
Final States ◽  
Independent Particle ◽  
Electron Momentum Spectroscopy ◽  
Independent Particle Model ◽  
Valence Bands ◽  
Momentum Space Orbitals

Electron momentum spectroscopy of atoms, molecules, and solids is based on (e,2e) reactions that observe the distribution of recoil momenta for energy-resolved states of the residual system. It is interpreted simply in terms of the momentum-space orbitals of the independent-particle model. The relevant ideas originated in nuclear physics. The earliest experiments observed that strongly excited final states belong to orbital manifolds that extend the independent-particle ideas to correlated systems. Some weakly excited final states do not belong to orbital manifolds. They give sensitive information about target ground-state correlations. The energy-momentum distribution of valence bands is observed for solids. Calculations for atoms, molecules, and crystals converge to the experimental result as the structure calculation is improved.

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