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.

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.

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.

Atomic Mechanisms of Grain Boundary Motion

2005 ◽  
Vol 502 ◽  
pp. 157-162 ◽  
Author(s):  
A. Suzuki ◽  
Yuri M. Mishin
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Geometric Model ◽  
Lattice Rotation ◽  
Shear Stresses ◽  
Translation Rate ◽  
Embedded Atom ◽  
Local Lattice ◽  
Symmetrical Tilt ◽  
Grain Boundary Motion

We present results of atomistic computer simulations of spontaneous and stress-induced grain boundary (GB) migration in copper. Several symmetrical tilt GBs have been studied using the embedded-atom method and molecular dynamics. The GBs are observed to spontaneously migrate in a random manner. This spontaneous GB motion is always accompanied by relative translations of the grains parallel to the GB plane. Furthermore, external shear stresses applied parallel to the GB and normal to the tilt axis induce GB migration. Strong coupling is observed between the normal GB velocity vn and the grain translation rate v||. The mechanism of GB motion is established to be local lattice rotation within the GB core that does not involve any GB diffusion or sliding. The coupling constant between vn and v|| predicted within a simple geometric model accurately matches the molecular dynamics observations.

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