Theoretical Investigation of Twist Boundaries in Germanium

1986 ◽  
Vol 77 ◽  
Author(s):  
M. C. Payne ◽  
P. D. Bristowe ◽  
J. D. Joannopoulos
Keyword(s):  
Molecular Dynamics ◽  
Simulated Annealing ◽  
Grain Boundary ◽  
Low Energy ◽  
Energy Structure ◽  
Microscopic Structure ◽  
Twist Boundary ◽  
Small Contraction ◽  
Annealing Method ◽  
Twist Boundaries

ABSTRACTResults of the first completely ab-initio investigation of the microscopic structure of a grain boundary in a semiconductor are presented. Using the molecular dynamics simulated annealing method for performing total energy calculations within the LDA and pseudopotential approximations, the σ=5(001) twist boundary in germanium is studied. A low energy structure is identified which exhibits a rigid body translation and a small contraction at the boundary.

scholarly journals Strength of Graphene-Coated Ni Bi-Crystals: A Molecular Dynamics Nano-Indentation Study

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1683
Author(s):  
Vardan Hoviki Vardanyan ◽  
Herbert M. Urbassek
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Composite Structure ◽  
Graphene Layer ◽  
Low Energy ◽  
Twist Boundary ◽  
Interface Failure ◽  
Nano Indentation ◽  
Graphene Composite ◽  
Interface Barrier

Nanoindentation simulations are performed for a Ni(111) bi-crystal, in which the grain boundary is coated by a graphene layer. We study both a weak and a strong interface, realized by a 30 ∘ and a 60 ∘ twist boundary, respectively, and compare our results for the composite also with those of an elemental Ni bi-crystal. We find hardening of the elemental Ni when a strong, i.e., low-energy, grain boundary is introduced, and softening for a weak grain boundary. For the strong grain boundary, the interface barrier strength felt by dislocations upon passing the interface is responsible for the hardening; for the weak grain boundary, confinement of the dislocations results in the weakening. For the Ni-graphene composite, we find in all cases a weakening influence that is caused by the graphene blocking the passage of dislocations and absorbing them. In addition, interface failure occurs when the indenter reaches the graphene, again weakening the composite structure.

The Relationship between the Microscopic Properties of Semiconducting Grain Boundaries and their Orientation

1990 ◽  
Vol 193 ◽  
Author(s):  
Eugen Tarnow ◽  
Tomas Arias ◽  
P. D. Bristowe ◽  
P. Dallot ◽  
G. P. Francis ◽  
...  
Keyword(s):  
Minimum Energy ◽  
Energy Structure ◽  
Energy Calculation ◽  
Microscopic Structure ◽  
Twist Boundary ◽  
Different Types ◽  
Tilt Boundaries ◽  
The Relationship ◽  
Theoretical Results ◽  
Twist Boundaries

ABSTRACTThe microscopic structure of a tilt and a twist boundary in germanium are explored using a state-of-the-art total energy calculation. The structure of the tilt boundary (Σ = 5 (310)) is found to be simple as it exhibits a well defined minimum energy structure, consistent with previous experimental and theoretical results on this and other tilt boundaries. The structure of the twist boundary (Σ = 5 (100)), however, is found to be very complex. The boundary bonds are distorted and weak, and their weakness makes the twist boundary exhibit a wealth of local energy minima. The different types of energy minima for the twist boundaries are identified and studied in some detail. We summarize the consequence of the orientation of the two crystal grains upon the microscopic structure of the boundaries, and speculate about future applications.

Cluster ‘Contact Epitaxy’- Direct Evidence for Novel Particle: Substrate Interactions

1999 ◽  
Vol 570 ◽  
Author(s):  
M. Yeadon ◽  
J.C. Yang ◽  
M. Ghaly ◽  
R.S. Averback ◽  
J.M. Gibson
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Grain Boundary ◽  
Ag Nanoparticles ◽  
Direct Evidence ◽  
Low Energy ◽  
Novel Interactions ◽  
Ag Cluster ◽  
Dynamics Simulations ◽  
Ordered Layers

ABSTRACTIn this paper we describe observations of novel interactions between clusters of Ag deposited on the clean (001) Cu surface. The experiments are analogous to those performed by Gleiter and co-workers in the 1970's, where grain boundary orientations in particles of Cu and Ag supported on single crystal metal substrates were studied. Upon annealing close to the melting point, these particles (∼10–100μm in diameter) were found to rotate on the surface, forming low-energy grain boundary configurations with the substrate. The particles studied in our experiments are ∼104 times smaller, and show rather different behavior. In the case of Ag nanoparticles we have observed a novel phenomenon, which we call ‘contact epitaxy’, involving the formation of several monolayers of epitaxially oriented Ag at the Cu surface upon contact between this surface and the Ag cluster. The phenomenon may be understood from molecular dynamics simulations of the ‘soft impact’ between the nanoparticle and surface, which indicate that the ordered layers form within picoseconds of contact. We will discuss the mechanisms by which ‘contact epitaxy’ is believed to occur.

Role of point defects in self-diffusion along low-angle twist boundaries in fcc metals: A molecular dynamics study

2018 ◽  
Vol 03 (01n02) ◽  
pp. 1850001 ◽  
Author(s):  
G. M. Poletaev ◽  
I. V. Zorya ◽  
M. D. Starostenkov
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Point Defects ◽  
Binding Energies ◽  
Fcc Metals ◽  
Self Diffusion ◽  
Thermodynamic Equilibrium Condition ◽  
Dynamics Method ◽  
Twist Boundaries

The interaction of point defects with low-angle (100), (110) and (111) twist boundaries in fcc metals Ni, Cu, Al and role of the point defects in self-diffusion along considered boundaries were studied by the molecular dynamics method. The binding energies of point defects with low-angle twist boundaries were calculated. It was found that the point defects are mainly fixed in the nodes of grain-boundary screw dislocations network. It was shown that the introduced vacancies play an important role in diffusion along twist grain boundaries. The contribution of introduced interstitial atoms to grain-boundary diffusion under thermodynamic equilibrium condition is less by several orders of magnitude in comparison with the contribution of vacancies.

A simulation study of self-assembly of ABC star terpolymers confined between two parallel surfaces

Soft Matter ◽  
2021 ◽  
Author(s):  
Zhiyao Liu ◽  
Zheng Wang ◽  
Yuhua Yin ◽  
Run Jiang ◽  
Baohui Li
Keyword(s):  
Simulated Annealing ◽  
Phase Behavior ◽  
Phase Diagrams ◽  
Simulation Study ◽  
Self Assembly ◽  
Simulated Annealing Method ◽  
Parallel Surfaces ◽  
Annealing Method

Phase behavior of ABC star terpolymers confined between two identical parallel surfaces is systematically studied with a simulated annealing method. Several phase diagrams are constructed for systems with different bulk...

scholarly journals Local Structuring of Diketopyrrolopyrrole (DPP)-based Oligomers from Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Maryam Reisjalali ◽  
J. Javier Burgos-Marmol ◽  
Rex Manurung ◽  
Alessandro Troisi
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
High Mobility ◽  
Semiconducting Polymers ◽  
Microscopic Structure ◽  
Dynamics Simulations

The microscopic structure of high mobility semiconducting polymers is known to be essential for their performance but it cannot be easily deduced from the available experimental data. A series of...

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