A Comparative Atomistic Study of the Structure of Grain Boundaries in Tungsten

1992 ◽  
Vol 291 ◽  
Author(s):  
A. Marinopoulos ◽  
M. Sob ◽  
V. Vitek ◽  
A. E. Carlsson
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Structural Characteristics ◽  
Many Body ◽  
Electronic Density ◽  
Atomic Interactions ◽  
Symmetrical Tilt ◽  
Tilt Grain Boundary ◽  
Atomistic Study ◽  
Central Forces

ABSTRACTMost atomistic studies of grain boundaries have been carried out using central forces to describe atomic interactions. However, in transition metals with unfilled d-bands the angular dependence of interatomic forces may be important. The purpose of this paper is to investigate the significance of angular forces in the case of Tungsten. The calculations have been performed for the Σ5(210) symmetrical tilt grain boundary using two alternate approaches. First are the central-force many-body potentials of the Finnis-Sinclair type. The second are the angular dependent potentials obtained via a moment analysis of the electronic density of states. The results of these two approaches are compared by analyzing the boundary structures, the relative displacements of the adjoining grains and the expansion. Differences in structural characteristics are discussed in terms of the effect of angular forces.

Ab-Initio Determination of the Atomic Structure of Symmetrical Tilt Grain Boundaries in BCC Transition Metals

1997 ◽  
Vol 492 ◽  
Author(s):  
C. Elsässer ◽  
O. Beck ◽  
T. Ochs ◽  
B. Meyer
Keyword(s):  
Transition Metals ◽  
Grain Boundary ◽  
Ab Initio ◽  
Grain Boundaries ◽  
Density Functional ◽  
Local Density ◽  
High Symmetry ◽  
Many Body ◽  
Local Density Functional Theory ◽  
Symmetrical Tilt

ABSTRACTAtomistic simulations of grain-boundary structures in body-centered cubic transition metals have revealed that angle-dependent contributions to interatomic interactions are essential. Unfortunately, the results of presently available empirical many-body potentials are not yet always sufficiently reliable for quantitative theoretical predictions of grain-boundary structures, which are consistent with experimental observations, e.g. by high-resolution transmission electron microscopy.Ab-initio electronic-structure calculations based on the local-density-functional theory offer the possibility to determine accurately the microscopic structures of special, high-symmetry grain boundaries, which can be used as data bases for the improvement of empirical many-body potentials. Such ab-initio calculations, with a mixed-basis pseudopotential method and grain-boundary supercells, are presented for Σ5 (310) [001] 36.87° symmetrical tilt grain boundaries in Niobium and Molybdenum.

Σ =13 tilt grain boundary in silicon bicrystal

1990 ◽  
Vol 48 (4) ◽  
pp. 562-563
Author(s):  
M.J. Kim ◽  
Y.L. Chen ◽  
R.W. Carpenter ◽  
J.C. Barry ◽  
G.H. Schwuttke
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rotation Axis ◽  
Czochralski Method ◽  
High Resolution Electron Microscopy ◽  
Image Simulation ◽  
Simulation Techniques ◽  
Resolution Electron ◽  
The Common ◽  
Tilt Grain Boundary

The structure of grain boundaries (GBs) in metals, semiconductors and ceramics is of considerable interest because of their influence on physical properties. Progress in understanding the structure of grain boundaries at the atomic level has been made by high resolution electron microscopy (HREM) . In the present study, a Σ=13, (510) <001>-tilt grain boundary in silicon was characterized by HREM in conjunction with digital image processing and computer image simulation techniques.The bicrystals were grown from the melt by the Czochralski method, using preoriented seeds. Specimens for TEM observations were cut from the bicrystals perpendicular to the common rotation axis of pure tilt grain boundary, and were mechanically dimpled and then ion-milled to electron transparency. The degree of misorientation between the common <001> axis of the bicrystal was measured by CBED in a Philips EM 400ST/FEG: it was found to be less than 1 mrad. HREM was performed at 200 kV in an ISI-002B and at 400 kv in a JEM-4000EX.

Structures of a Σ = 9, [110]/{221} symmetrical tilt grain boundary in SrTiO3

2011 ◽  
Vol 46 (12) ◽  
pp. 4162-4168 ◽  
Author(s):  
T. Mitsuma ◽  
T. Tohei ◽  
N. Shibata ◽  
T. Mizoguchi ◽  
T. Yamamoto ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Symmetrical Tilt ◽  
Tilt Grain Boundary

Interaction Between Lattice Dislocations and Grain Boundaries In Ordered Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
B.J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.W. Schapink
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Shockley Partial Dislocation ◽  
Screw Dislocations ◽  
Applied Shear Stress ◽  
Tilt Boundaries

ABSTRACTThe interaction of 1/2<1 1 0> screw dislocations with symmetric [1 1 0] tilt boundaries was investigated by atomistic simulations using many-body potentials representing ordered compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the interaction in ordered compounds shows similarities to the interaction in fcc.

Atomistic Modeling of Extended Defects in Metalic Alloys: Dislocations and Grain Boundaries in Ll2 Compounds

1990 ◽  
Vol 186 ◽  
Author(s):  
V. Vitek ◽  
G. J. Ackland ◽  
J. Cserti
Keyword(s):  
Grain Boundaries ◽  
Dislocation Core ◽  
Extended Defects ◽  
Atomistic Modeling ◽  
Many Body ◽  
Deformation And Fracture ◽  
Governing Factor ◽  
Atomic Interactions ◽  
Total Energies ◽  
Physical Features

AbstractExtended defects, such as dislocations and grain boundaries, control a wide variety of material properties and their atomic structure is often a governing factor. A necessary precursor for modeling of these structures is a suitable description of atomic interactions. We present here empirical many-body potentials for alloys which represent a very simple scheme for the evaluation of total energies and yet reflect correctly the basic physical features of the alloy systems modeled. As examples of atomistic studies we show results of calculations of the core structures of screw dislocations in Ll2 compounds. The same potentials have also been used to calculate structures of grain boundaries in these compounds. The deformation and fracture behavior of Ll2 alloys is then discussed in the light of grain boundary and dislocation core studies.

HTREM Studies of Segregated Ga at the Al Sigma 11 (113)[11―0] Symmetrical Tilt Grain Boundary

2004 ◽  
Vol 10 (S02) ◽  
pp. 282-283
Author(s):  
Gunther Richter ◽  
Steffen Schmidt ◽  
Wilfried Sigle ◽  
Manfred Rühle
Keyword(s):  
Grain Boundary ◽  
Symmetrical Tilt ◽  
Tilt Grain Boundary

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Theoretical Study of Polar and Non-Polar Interfaces in Compound Semiconductors: A Thermodynamic Analysis Based on Electronic Structure Calculations

1992 ◽  
Vol 278 ◽  
Author(s):  
M. Kohyama ◽  
S. Kose ◽  
R. Yamamoto
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Compound Semiconductors ◽  
Binding Energies ◽  
Chemical Potentials ◽  
Zinc Blende ◽  
Thermodynamic Potentials ◽  
Symmetrical Tilt ◽  
The Stability ◽  
Structure Calculations

AbstractPolar and non-polar interfaces of grain boundaries in compound semiconductors can be defined by the stoichlometry in the interface region, and It Is possible to construct two polar and one non-polar Interfaces for a symmetrical tilt grain boundary In the zinc-blende structure of which the Interface Is polar surfaces. The atomic and electronic structures of polar and non-polar interfaces of the {122} Σ=9 grain boundary in SIC have been examined by using the SCTB method coupled with the supercell technique. By using the calculated binding energies, the relative stability of the polar and non-polar interfaces has been analyzed through calculations of the thermodynamic potentials as a function of the atomic chemical potentials. It has been shown that the wrong bonds and the stoichlometry much Influence the stability and properties of grain boundaries in SiC. The stability of polar Interfaces In heterovalent compound semiconductors has been discussed.

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