Structure of Dislocation Cores in GaAs

2003 ◽  
Vol 779 ◽  
Author(s):  
S. P. Beckman ◽  
D. C. Chrzan
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Ab Initio ◽  
Partial Dislocation ◽  
Atomic Scale ◽  
The Core ◽  
Partial Dislocations ◽  
Double Period ◽  
Single Period ◽  
Scale Structures

AbstractThe atomic scale structures of the partial dislocation cores in GaAs are explored using ab initio electronic structure total energy techniques. The structure of the 30° partial dislocations are expected to be period doubled along the core. The structure of the 90° partial dislocations remains more uncertain, and here, an effort is made to predict which of two proposed reconstruction, double period or single period, is more stable. The relative energies of the two core structures are found to be equal, within the accuracy of the present calculations. It is suggested that at temperature, both core reconstructions will be present.

Effect of Chromium and Vanadium on Nanolayered Ternary Carbides: AB Initio Study

2009 ◽  
Vol 609 ◽  
pp. 239-242
Author(s):  
A.E. Merad ◽  
M.B. Kanoun
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Ab Initio ◽  
Structural Parameters ◽  
Ab Initio Study ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Full Relaxation ◽  
Relaxation Procedure ◽  
Ternary Carbides

The Cr2AlC and V2AlC nanolayered ternary carbides are studied by performing APW-lo ab initio total energy calculations within the recent Wu-Cohen generalized gradient approximation GGA. Using full relaxation procedure of the volume and the atomic positions we obtained the structural parameters and electronic structure of the optimization hexagonal. Results were compared with the experimental ones. Interesting features are deduced. In fact, we have shown why these materials are conductors.

A large angle convergent beam electron diffraction study of the core nature of dislocations in 3C-SiC

1996 ◽  
Vol 11 (4) ◽  
pp. 884-894 ◽  
Author(s):  
X. J. Ning ◽  
P. Pirouz
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Partial Dislocation ◽  
Large Angle ◽  
Electron Diffraction Study ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
The Core ◽  
Partial Dislocations ◽  
Convergent Beam

Dislocations produced by 1300 °C indentation of the silicon-terminated (111) face of 3C-SiC were investigated by transmission electron microscopy. They were all found to be either widely separated partial dislocation pairs, or else, arrays of single partial dislocation half-loops on neighboring parallel slip planes and having the same Burgers vector. It was concluded that in the latter case, each array consisted of leading partial dislocations which had nucleated without accompanying trailing partial dislocations. The core nature of both dissociated dislocations and arrays of single partial dislocations has been determined by the technique of large angle convergent beam electron diffraction. The results indicate that the core of all single partial dislocation half-loops constituting an array consists of silicon atoms. It is concluded that, with the present deformation geometry, the Si-core partial dislocations are preferentially nucleated before the C-core partial dislocations. In the case of a dissociated dislocation, when a pair of partials was present, electron microscopy observations revealed that the morphology of the two partial dislocations was very different; while the Si-core partials were smooth, the C-core partial dislocations had a zig-zag morphology.

First-Principles Calculations of the Elastic Properties of the Nickel-Based L12 Intermetallics

1995 ◽  
Vol 408 ◽  
Author(s):  
D. Iotova ◽  
N. Kioussis ◽  
S. P. Lim ◽  
S. Sun ◽  
R. Wu
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Ab Initio ◽  
Elastic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Anisotropy Factor ◽  
Full Potential ◽  
First Principles Calculations ◽  
Linear Muffin Tin Orbital

AbstractThe elastic constants of the L12-type ordered nickel-based intermetallics Ni3X (X = Mn, Al, Ga, Si, Ge), have been calculated by means of ab initio total-energy electronic structurecalculations based on the full-potential linear-muffin-tin-orbital (FLMTO) method. Theorigins in the electronic structure of the variation of the elastic constants, bulk and shearmoduli are investigated across the series, and the effects of the anisotropy of bonding chargedensity on the shear anisotropy factor and the degree of ductility is discussed.

Zur geometrischen Struktur von CF5−, — eine wellenmechanische Untersuchung / The Geometrical Structure of CF0− , a Wave Mechanical Investigation

1973 ◽  
Vol 28 (11) ◽  
pp. 1832-1835
Author(s):  
S.-J. Wang
Keyword(s):  
Carbon Atom ◽  
Total Energy ◽  
Ab Initio ◽  
Geometrical Structure ◽  
Variation Method ◽  
The Core ◽  
Trigonal Bipyramidal ◽  
Bipyramidal Structure ◽  
Mechanical Investigation ◽  
Energy Variation Method

The geometrical structure of CF5− has been ab initio investigated, taking all 52 electrons into account, using the MOLPRO-Programm/SCF-MO-LC-(LCGO)-Method. After approximating the core by means of the energy variation method and varying the ηp-values and the C - F-distance a total energy of - 517,7008 a. u. with a C - F4,5-distance of 2.78 a. u. and a C - F1,2,3 -distance of 2.74 a. u. for the CF5−-system of the trigonal bipyramidal structure was found.Likewise a total energy of -517.7036 a. u. with a C - F -distance of 2.58 a. u. in the tetraedral CF4 and a CF4 - F−-distance of 5.80 a. u. for the CF4 -F−-system was found. The best C-F-distance of the tetraedral CF4 was given at a distance of 2.51 a. u.According to this investigation it can be concluded that the structure of the system CF4 - F− is the most stable one. An interesting result through the analysis of the electrondistribution is that the carbon atom is almost in all structure systems nearly unchanged.

Theory of Dislocations in SiC: The Effect of Charge on Kink Migration

2006 ◽  
Vol 527-529 ◽  
pp. 321-326
Author(s):  
T.A.G. Eberlein ◽  
R. Jones ◽  
A.T. Blumenau
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Forward Bias ◽  
Compound Semiconductors ◽  
Stacking Fault ◽  
Computing Power ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Fault Growth ◽  
Atomic And Electronic Structure

Under forward bias bipolar 4H- and 6H-SiC devices are known to degrade rapidly through stacking fault formation and expansion in the basal plane. It is believed that the ob- served rapid stacking fault growth is due to a recombination-enhanced dislocation glide (REDG) mechanism at the bordering partial dislocations. This degradation phenomenon has generated considerable interest in the involved dislocations — in particular in their atomic and electronic structure, but also in the mechanisms of their glide motion. Fortunately, nowadays advances in computing power and in theoretical methodology allow the ab initio based modelling of some aspects of the problem. This paper therefore gives a brief review of recent activities in this field, and further discusses some general problems of ab initio based modelling of dislocations in compound semiconductors.

An Ab Initio Investigation of a Grain Boundary in a Transition Metal Oxide

1995 ◽  
Vol 408 ◽  
Author(s):  
I. Dawson ◽  
P. D. Bristowe. ◽  
M. C. Payne ◽  
M-H. Lee
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Grain Boundary ◽  
Metal Oxide ◽  
Total Energy ◽  
Ab Initio ◽  
Transition Metal Oxide ◽  
The Stability ◽  
Energy Plane ◽  
Translation State

AbstractWe have used ab initio total energy plane wave pseudopotential methods to perform the first completely ab initio investigation of the atomic and electronic structure of a grain boundary in a transition metal oxide. The ∑ = 15 (210)[001] tilt boundary in rutile TiG2 is studied using the conjugate gradients iterative minimisation technique for performing total energy calculations within the LDA and pseudopotential approximations. The stability of the experimentally observed translation state of the boundary is confirmed, and some insight is gained into its electronic structure.

Electronic structure and optical properties of CuWO4: An ab initio study

2012 ◽  
Vol 63 ◽  
pp. 163-167 ◽  
Author(s):  
M.V. Lalić ◽  
Z.S. Popović ◽  
F.R. Vukajlović
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Ab Initio ◽  
Ab Initio Study
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