scholarly journals Defects and dislocations in MgO: atomic scale models of impurity segregation and fast pipe diffusion

2010 ◽  
Vol 20 (46) ◽  
pp. 10445 ◽  
Author(s):  
Feiwu Zhang ◽  
Andrew M. Walker ◽  
Kate Wright ◽  
Julian D. Gale
Keyword(s):  
Atomic Scale ◽  
Pipe Diffusion ◽  
Impurity Segregation ◽  
Scale Models

scholarly journals Atomic-scale models of dislocation cores in minerals: progress and prospects

2010 ◽  
Vol 74 (3) ◽  
pp. 381-413 ◽  
Author(s):  
A. M. Walker ◽  
P. Carrez ◽  
P. Cordier
Keyword(s):  
Plastic Deformation ◽  
Atomic Scale ◽  
Elastic Displacement ◽  
Atomistic Model ◽  
Pipe Diffusion ◽  
Burgers Vector ◽  
The Core ◽  
Super Cell ◽  
Scale Models ◽  
Mechanisms Of Plastic Deformation

AbstractRecent advances in computer simulation at the atomic scale have made it possible to probe the structure and behaviour of the cores of dislocations in minerals. Such simulation offers the possibility to understand and predict the dislocation-mediated properties of minerals such as mechanisms of plastic deformation, pipe diffusion and crystal growth. In this review the three major methods available for the simulation of dislocation cores are described and compared. The methods are: (1) cluster-based models which combine continuum elastic theory of the extended crystal with an atomistic model of the core; (2) dipole models which seek to cancel the long-range elastic displacement caused by the dislocation by arranging for the simulation to contain several dislocations with zero net Burgers vector, thus allowing a fully periodic super-cell calculation; and (3) the Peierls-Nabarro approach which attempts to recast the problem so that it can be solved using only continuum-based methods, but parameterizes the model using results from atomic-scale calculations. The strengths of these methods are compared and illustrated by some of the recent studies of dislocations in mantle silicate minerals. Some of the unresolved problems in the field are discussed.

Atomistic Aspects of Fracture Modelling in the Framework of Continuum Mechanics

1998 ◽  
Vol 538 ◽  
Author(s):  
F. Cleri
Keyword(s):  
Continuum Mechanics ◽  
Constitutive Relations ◽  
Point Of View ◽  
Atomic Scale ◽  
Continuum Models ◽  
Cohesive Law ◽  
Macroscopic Models ◽  
Scale Models ◽  
Level Information ◽  
Set Up

AbstractThe validity and predictive capability of continuum models of fracture rests on basic informations whose origin lies at the atomic scale. Examples of such crucial informations are, e.g., the explicit form of the cohesive law in the Barenblatt model and the shear-displacement relation in the Rice-Peierls-Nabarro model. Modem approaches to incorporate atomic-level information into fracture modelling require to increase the size of atomic-scale models up to millions of atoms and more; or to connect directly atomistic and macroscopic, e.g. finite-elements, models; or to pass information from atomistic to continuum models in the form of constitutive relations. A main drawback of the atomistic methods is the complexity of the simulation results, which can be rather difficult to rationalize in the framework of classical, continuum fracture mechanics. We critically discuss the main issues in the atomistic simulation of fracture problems (and dislocations, to some extent); our objective is to indicate how to set up atomistic simulations which represent well-posed problems also from the point of view of continuum mechanics, so as to ease the connection between atomistic information and macroscopic models of fracture.

scholarly journals Atomic scale models of Ion implantation and dopant diffusion in silicon

10.2172/12209 ◽  
1999 ◽  
Author(s):  
M Caturla ◽  
M Johnson ◽  
T Lenosky ◽  
B Sadigh ◽  
S K Theiss ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Atomic Scale ◽  
Dopant Diffusion ◽  
Scale Models

scholarly journals Atomic-scale description of interfaces in rutile/sodium silicate glass–crystal composites

2018 ◽  
Vol 20 (26) ◽  
pp. 17624-17636 ◽  
Author(s):  
Paul C. M. Fossati ◽  
Michael J. D. Rushton ◽  
William E. Lee
Keyword(s):  
Crystal Structure ◽  
Sodium Silicate ◽  
Silicate Glass ◽  
Glass Phase ◽  
Structural Changes ◽  
Atomic Scale ◽  
Sodium Silicate Glass ◽  
Scale Models ◽  
Glass Crystal ◽  
Crystal Interfaces

Investigations of glass/crystal interfaces using atomic-scale models underlined structural changes in the glass phase as it accommodates the underlying crystal structure.

Atomic-scale models of early-stage alkali depletion and SiO2-rich gel formation in bioactive glasses

2015 ◽  
Vol 17 (4) ◽  
pp. 2696-2702 ◽  
Author(s):  
Antonio Tilocca
Keyword(s):  
Molecular Dynamics ◽  
Early Stage ◽  
Atomic Scale ◽  
Gel Formation ◽  
Gel Structure ◽  
Bioactive Glasses ◽  
Direct Mechanism ◽  
Scale Models ◽  
Dynamics Simulations ◽  
45S5 Bioglass

Molecular dynamics simulations of Na+/H+-exchanged 45S5 Bioglass® reveal the co-existence of bonded and non-bonded hydroxyls, suggesting a direct mechanism for forming a silica-rich gel structure upon the initial ion exchange.

Quantitative Determination of Bi Segregation at Grain Boundaries in Cu Bicrystals

1997 ◽  
Vol 3 (S2) ◽  
pp. 535-536
Author(s):  
U. Alber ◽  
H. Müllejans ◽  
M. Rühle
Keyword(s):  
Electron Beam ◽  
Grain Boundaries ◽  
Primary Electron ◽  
Atomic Scale ◽  
Beam Diameter ◽  
Primary Electron Beam ◽  
Impurity Segregation ◽  
A Value ◽  
Bi Segregation ◽  
Beam Broadening

Impurity segregation at grain boundaries (GB) can be detected by EDS in a dedicated STEM. Quantification of the segregation requires not only quantification of the spectra but also consideration of the geometry of the experiment. Our aim was to obtain a value which characterises only the segregation of the impurity and is independent of experimental parameters. The problem is that the specimen composition at the GB is extremely inhomogeneous on an atomic scale in the case of Bi segregation at GBs in Cu. The analysed volume which is defined by the irradiated area and the beam broadening of the primary electron beam inside the specimen contains the interfacial plane as well as neighbouring bulk Cu. One approach is to put the focussed primary electron beam on the interface which is aligned edge on and acquire a spectrum. Both the primary beam diameter and the beam broadening inside the specimen have to be known.

scholarly journals Atomic Scale Models for Grain Boundary Potentials in Perovskites

2002 ◽  
Vol 8 (S02) ◽  
pp. 578-579
Author(s):  
R.F. Klie ◽  
J. P. Buban ◽  
N. D. Browning
Keyword(s):  
Grain Boundary ◽  
Atomic Scale ◽  
Scale Models
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