Atomic Structure of the (310) Twin in Niobium: Theoretical Predictions and Comparison with Experimental Observation

1992 ◽  
Vol 295 ◽  
Author(s):  
Geoffrey H. Campbell ◽  
S. M. Foiles ◽  
M. Rühle ◽  
W. E. King
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Atomic Structure ◽  
Mirror Symmetry ◽  
Interatomic Potentials ◽  
Pseudopotential Theory ◽  
Embedded Atom ◽  
Transmission Electron ◽  
Theoretical Predictions ◽  
Model Structures

AbstractHigh - resolution transmission electron microscopy (HREM) has been used to characterize the atomic structure of the symmetric 36.9° tilt grain boundary with [001] tilt axes forming a twin about (310) in Nb. The projected structure was imaged along two different directions in the plane of the boundary and was compared to model structures through high - resolution image simulation. The atomic structure of this Σ5 boundary was predicted with atomistic simulations using interatomic potentials derived from the Embedded Atom Method (EAM), Finnis-Sinclair (FS), and the Model Generalized Pseudopotential Theory (MGPT). The EAM and FS predicted structures with translations of the adjacent crystals which break mirror symmetry. The MGPT predicted one stable structure with mirror symmetry. The atomic structure of the (310) twin in Nb was found by HREM to be mirror symmetric. These findings indicate that the angular dependent interactions modeled in the MGPT are important for determining the grain boundary structures of bcc transition metals.

Hrem Investigation of the Structure of the σ5(310)/[001] Symmetric Tilt Grain Boundary In Nb.*

1990 ◽  
Vol 209 ◽  
Author(s):  
Wayne E. King ◽  
G. H. Campbell ◽  
A. Coombs ◽  
M. J. Mills ◽  
M. RüHle
Keyword(s):  
Grain Boundary ◽  
High Vacuum ◽  
High Resolution Electron Microscopy ◽  
Ultra High Vacuum ◽  
Interatomic Potentials ◽  
Pseudopotential Theory ◽  
Tilt Axis ◽  
Embedded Atom ◽  
Symmetric Tilt ◽  
Bonding Method

ABSTRACTRecent atomistic simulations using interatomic potentials for Nb developed employing the embedded atom method (EAM) and the model generalized pseudopotential theory (MGPT) have indicated a possible cusp at the Σ5(310) orientation in the energy vs tilt angle curves for<001> symmetric tilt grain boundaries. In addition, the most stable structure predicted using EAM exhibits shifts of one crystal relative to the other along the tilt axis and along the direction perpendicular to the tilt axis lying in the boundary plane. The structure predicted using the MGPT was mirror symmetric across the plane of the grain boundary. This boundary has been prepared for experimental study using the ultra high vacuum diffusion bonding method. A segment of this boundary has been studied using high resolution electron microscopy.

Diffusion, Migration and the Atomic Structure of some Grain Boundaries

1985 ◽  
Vol 57 ◽  
Author(s):  
W. Krakow ◽  
D. A. Smith
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Atomic Structure ◽  
Boundary Diffusion ◽  
Transmission Electron ◽  
Diffusion Migration ◽  
Tilt Boundaries ◽  
And Migration

AbstractThe atomic structure of representative tilt boundaries in gold has been determined by high resolution transmission electron microscopy. Characteristic and varying regions of decreased density and coordination have been identified and related to mechanisms of grain boundary diffusion and migration

Atomic Structure OF YΣ=5 (130) Symmetrical Tilt Boundary In Strontium Titanate

1992 ◽  
Vol 295 ◽  
Author(s):  
V. Ravikumar ◽  
Vinayak P. Dravid
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Strontium Titanate ◽  
Atomic Structure ◽  
Coincidence Site Lattice ◽  
Tilt Boundary ◽  
Transmission Electron ◽  
Resolution Electron

AbstractThe atomic structure of a pristine (undoped) boundary in strontium titanate has been investigated using transmission electron microscopy techniques. Results of electron diffraction studies indicate a pure tilt boundary with a common \001] tilt axis, and a tilt angle of 36.8°, which corresponds to a Σ-= 5 grain boundary in the Coincidence Site Lattice (CSL) notation. High Resolution Transmission Electron Microscopy (HRTEM) indicates a symmetric tilt grain boundary with a (130) type grain boundary plane. No cation non-stoichiometry or impurity segregants could be detected at the interface, within the limits of the Energy Dispersive X-ray microanalysis technique used. The grain boundary has a compact core, with negligible planenormal rigid body translation (RBT). An in-plane RBT of (1/2)d130 (˜ 0.62 A°) was identified from the high resolution electron micrographs. An empirical model of the relaxed atomic structure of the grain boundary is proposed.

Atomic-Scale Processes of Grain-Boundary Faceting in a Zirconia Bicrystal

2007 ◽  
Vol 558-559 ◽  
pp. 955-958
Author(s):  
Naoya Shibata ◽  
Fumiyasu Oba ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Atomic Structure ◽  
Boundary Plane ◽  
Atomic Scale ◽  
Transmission Electron ◽  
Facet Growth ◽  
Boundary Core

In this paper, we characterized atomic structure of a Σ = 3, [110]/{112} grain boundary in a yttria-stabilized cubic zirconia bicrystal. High-resolution transmission electron microscopy (HRTEM) clearly revealed that the grain boundary migrated to form {111}/{115} periodical facets, although the bicrystal was initially joined so as to have the symmetric straight boundary plane of {112}. Atomic-scale process for the facet growth could be modeled by the continuous flippings of atoms at the boundary core.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

The Study of Defects in Metals Using High Resolution Transmission Electron Microscopy and Atomistic Calculations

1990 ◽  
Vol 183 ◽  
Author(s):  
M. J. Mills ◽  
M. S. Daw
Keyword(s):  
Grain Boundary ◽  
Good Description ◽  
Dislocation Core ◽  
Thin Foil ◽  
Core Structure ◽  
Embedded Atom ◽  
Pair Potentials ◽  
Transmission Electron ◽  
Atomistic Calculations ◽  
Stringent Test

AbstractThe coupling of HRTEM with atomistic calculations is described for the study of grain boundaries and dislocations in aluminum. HRTEM images of the Σ9 (221) [110] grain boundary are compared with molecular statics calculations using both the Embedded Atom Method (EAM) and two pair potentials. Comparison between observed and simulated images are shown to serve as a stringent test of the theoretical methods. Atomistic calculations can in turn provide threedimensional information about the defect structure. Using the EAM, it is also possible to account for the effects of thin foil geometries on the minimim energy configuration of defects. While these effects are found to be minimal for grain boundary structures, the influence of the thin-foil geometries on the core structure of the 60° dislocation in aluminum is discussed. These comparisons indicate that the EAM function provides a good description of grain boundary structures, but fails to reproduce the observed dislocation core structure due to a low predicted value of the intrinsic stacking fault energy (SFE) on the (111). In contrast, the pair potentials used in this study provide reasonable SFE values, but appear to be less accurate for the prediction of the Σ9 (221) [110] grain boundary structures.

High-Resolution Transmission Electron Microscopy Studies of a Near Sigma11 Grain Boundary in alpha-Alumina

1994 ◽  
Vol 77 (2) ◽  
pp. 339-348 ◽  
Author(s):  
Thomas Hoche ◽  
Philip R. Kenway ◽  
Hans-Joachim Kleebe ◽  
Manfred Ruhle ◽  
Patricia A. Morris
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Transmission Electron ◽  
Alpha Alumina

Effect of Ge-rich Si1−zGez Segregation on the Morphological Stability of NiSi1−uGeu Film Formed on Strained (001) Si0.8Ge0.2 Epilayer

2004 ◽  
Vol 810 ◽  
Author(s):  
H.B. Yao ◽  
D.Z. Chi ◽  
S. Tripathy ◽  
S.Y. Chow ◽  
W.D. Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Surface Morphology ◽  
Morphological Stability ◽  
Triple Junctions ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Segregation Process

ABSTRACTThe germanosilicidation of Ni on strained (001) Si0.8Ge0.2, particularly Ge segregation, grain boundary grooving, and surface morphology, during rapid thermal annealing (RTA) was studied. High-resolution cross-sectional transmission electron microscopy (HRXTEM) suggested that Ge-rich Si1−zGez segregation takes place preferentially at the germanosilicide/Si1−xGex interface, more specifically at the triple junctions between two adjacent NiSi1−uGeu grains and the underlying epi Si1−xGex, and it is accompanied with thermal grooving process. The segregation process accelerates the thermal grooving of NiSi1−uGeu grain boundaries at the interface. The segregation-accelerated grain boundary grooving has significant effect on the surface morphology of NiSi1−uGeu films in Ni-SiGe system.

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