Theoretical study of the electronic structure of a high-angle tilt grain boundary in Si

1984 ◽  
Vol 29 (2) ◽  
pp. 889-892 ◽  
Author(s):  
R. E. Thomson ◽  
D. J. Chadi
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Theoretical Study ◽  
High Angle ◽  
Tilt Grain Boundary

Atomistic Aspects of Crack Propagation Along High Angle Grain Boundaries

1996 ◽  
Vol 460 ◽  
Author(s):  
Diana Farkas
Keyword(s):  
Grain Boundary ◽  
Atomistic Simulations ◽  
High Angle ◽  
Brittle Behavior ◽  
Embedded Atom ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
Grain Boundary Fracture ◽  
Tilt Grain Boundary ◽  
Boundary Fracture

ABSTRACTWe present atomistic simulations of the crack tip configuration near a high angle Σ= 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

Theoretical study of the electronic structure of the incoherent {211} Σ=3 grain boundary in Ge by the recursion approach

1987 ◽  
Vol 35 (3) ◽  
pp. 1267-1272 ◽  
Author(s):  
A. Mauger ◽  
J. Bourgoin ◽  
G. Allan ◽  
M. Lannoo ◽  
A. Bourret ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Theoretical Study

Ab Initio Electronic Structure Calculations of the Σ 5 (210) [001] Tilt Grain Boundary in Ni3Al

1997 ◽  
Vol 472 ◽  
Author(s):  
Gang Lu ◽  
Nicholas Kioussis
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Boundary Energy ◽  
Boundary Region ◽  
Embedded Atom Method ◽  
Full Potential ◽  
Plane Wave Method ◽  
Embedded Atom ◽  
Tilt Grain Boundary ◽  
Linearized Augmented Plane Wave

ABSTRACTThe atomic and the electronic structure of the Σ 5 (210) [001] tilt grain boundary in Ni3Al have been calculated using the full potential linearized-augmented plane-wave method. The strain field normal to the boundary plane and the excess grain boundary volume are calculated and compared with the results obtained using the embedded-atom method (EAM). The interlayer strain normal to the grain boundary oscillates with increasing distance from the grain boundary. The bonding charge distributions suggest that bonding in the boundary region is significantly different from that in the bulk. The grain boundary energy and the Griffith cohesive energy are calculated and compared with the EAM results.

Al Grain Boundary Embrittlement Promoted by Na Impurity: An ab initio Study

2000 ◽  
Vol 653 ◽  
Author(s):  
Guang-Hong Lu ◽  
Masanori Kohyama ◽  
Rayoichi Yamamoto
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Charge Density ◽  
First Principles ◽  
Ab Initio Study ◽  
Impurity Atoms ◽  
Metallic Bond ◽  
Tilt Grain Boundary ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

AbstractWe calculate the electronic structure of AlΣ9 tilt grain boundary with substitutional Na impurity atoms by first principles pseudopotential method. Results show that by Na segregation Al grain boundary expands and the valence charge density decreases significantly along the boundary. There is no stronger bond than metallic bond in the boundary even with Na impurity. We therefore conclude that the mechanism of Na-promoted Al grain boundary embrittlement should be one kind of ‘decohesion model’.

An ab initio Investigation on the Effects of Impurity in Aluminum Grain Boundary

2001 ◽  
Vol 699 ◽  
Author(s):  
Guang-Hong Lu ◽  
Tomoyuki Tamura ◽  
Masao Kamiko ◽  
Masanori Kohyama ◽  
Ryoichi Yamamoto
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Charge Density ◽  
Ab Initio ◽  
Mobility Model ◽  
Weak Bond ◽  
Impurity Atoms ◽  
Tilt Grain Boundary ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

AbstractThe electronic structure of AlS9 tilt grain boundary with segregated impurity atoms of Na, Ca, Si and S, respectively, has been investigated by an ab initio pseudopotential method. Na and Ca segregation causes the boundary to expand and the charge density to decrease significantly. There forms several weak bond regions. Si segregation increases the charge density between Si and the neighboring Al atom. There forms a stronger Al-Si bond that is a mixture of covalent and metallic character in the boundary. For S segregation, though there forms the stronger bond between Al and S atom, some Al-S bonds may become weaker than the former Al-Al bonds because of the charge density decrease. It is concluded that the mechanism of Na or Ca-promoted Al grain boundary embrittlement is one kind of ‘decohesion model’, that of Si is ‘bond mobility model’. It can't be decided the embrittlement mechanism by S segregation is classified into ‘bond mobility model’ or ‘decohesion model’.

Defects in the Structure of Σ=27 Tilt Grain-Boundaries in Ge.

1990 ◽  
Vol 209 ◽  
Author(s):  
Stuart Mckernan ◽  
C. Barry Carter ◽  
Zvi Elgat
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Screw Dislocation ◽  
Structural Unit ◽  
Boundary Plane ◽  
High Angle ◽  
Structural Units ◽  
Short Segment ◽  
Tilt Boundaries ◽  
Tilt Grain Boundary

ABSTRACTGeneral high-angle tilt grain-boundaries may be described by an arrangement of repeating structural units. A particular defect in the normal arrangement of structural units in a Σ=27 <110> tilt grain-boundary in Ge is reported.The defect is characterized by a short segment of (111) facet at the interface, and is associated with a screw dislocation in the boundary plane. This defect accommodates a slight misorientation of the boundary away from the perfect tilt configuration, andmay represent a type of structural unit present in other tilt boundaries containing a small twist component.

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