Non-Nearest Neighbor MD Boundary Condition

Comparison between Vortex-In-Cell and Vortex Particle Methods on Two-Dimensional Problem

AVIA ◽

10.47355/avia.v3i1.40 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

C X Canh ◽

L R Zuhal ◽

H Muhammad

Keyword(s):

Boundary Condition ◽

Numerical Methods ◽

Nearest Neighbor ◽

Particle Method ◽

Vortex Method ◽

Particle Methods ◽

Immersed Boundary ◽

Two Dimensional ◽

N Body Problem ◽

Vortex Particle

This research is concerned with the two-dimensional vortex method (VM) solvers. We develop and investigate the performance of the Vortex-In-Cell (VIC) and Vortex Particle Method (VPM) which are well known as the VM’s family members. The advantage of these both methods are that we can accelerate velocity computation procedure, an N-body problem in numerical methods, by using Fast Fourier Transform (FFT) and Fast Multipole Method (FMM), respectively. In addition, the viscous calculation process in VPM can be accelerated by using a scheme of Nearest Neighbor Particle Searching (NNPS) algorithms. Moreover, the no-through boundary condition treatment issue can be easily handled by using an immersed boundary condition for both methods. The accuracy and numerical cost of both numerical methods will be examined by simulating flow over an Impulsively Started Circular Cylinder and comparisons

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Discrete-to-continuum limits of planar disclinations

ESAIM Control Optimisation and Calculus of Variations ◽

10.1051/cocv/2021025 ◽

2021 ◽

Vol 27 ◽

pp. 23

Author(s):

Pierluigi Cesana ◽

Patrick van Meurs

Keyword(s):

Boundary Condition ◽

Nearest Neighbor ◽

Materials Science ◽

Additional Term ◽

Density Theorem ◽

Special Boundary ◽

Relaxation Methods ◽

Planar Domains ◽

Special Boundary Condition ◽

Numerical Minimization

In materials science, wedge disclinations are defects caused by angular mismatches in the crystallographic lattice. To describe such disclinations, we introduce an atomistic model in planar domains. This model is given by a nearest-neighbor-type energy for the atomic bonds with an additional term to penalize change in volume. We enforce the appearance of disclinations by means of a special boundary condition. Our main result is the discrete-to-continuum limit of this energy as the lattice size tends to zero. Our proof relies on energy relaxation methods. The main mathematical novelty of our proof is a density theorem for the special boundary condition. In addition to our limit theorem, we construct examples of planar disclinations as solutions to numerical minimization of the model and show that classical results for wedge disclinations are recovered by our analysis.

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Observation of Superlattice Dislocations on Cube Planes in Ni3Al

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071314 ◽

1973 ◽

Vol 31 ◽

pp. 174-175 ◽

Cited By ~ 1

Author(s):

J. M. Oblak ◽

W. H. Rand

Keyword(s):

Nearest Neighbor ◽

Antiphase Boundary ◽

Nearest Neighbors ◽

High Energy ◽

Cross Slip ◽

Octahedral Plane ◽

Trapping Mechanism ◽

Slip Traces

The energy of an a/2 <110> shear antiphase. boundary in the Ll2 expected to be at a minimum on {100} cube planes because here strue ture is there is no violation of nearest-neighbor order. The latter however does involve the disruption of second nearest neighbors. It has been suggested that cross slip of paired a/2 <110> dislocations from octahedral onto cube planes is an important dislocation trapping mechanism in Ni3Al; furthermore, slip traces consistent with cube slip are observed above 920°K.Due to the high energy of the {111} antiphase boundary (> 200 mJ/m2), paired a/2 <110> dislocations are tightly constricted on the octahedral plane and cannot be individually resolved.

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Application of Lattice Imaging Techniques to Amorphous Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113664 ◽

1975 ◽

Vol 33 ◽

pp. 8-9

Author(s):

S. R. Herd ◽

P. Chaudhari

Keyword(s):

Nearest Neighbor ◽

Random Network ◽

Imaging Techniques ◽

Network Models ◽

Accurate Method ◽

Direct Transmission ◽

Lattice Imaging ◽

Transmission Electron ◽

Lattice Planes ◽

Nearest Neighbor Distances

Electron diffraction and direct transmission have been used extensively to study the local atomic arrangement in amorphous solids and in particular Ge. Nearest neighbor distances had been calculated from E.D. profiles and the results have been interpreted in terms of the microcrystalline or the random network models. Direct transmission electron microscopy appears the most direct and accurate method to resolve this issue since the spacial resolution of the better instruments are of the order of 3Å. In particular the tilted beam interference method is used regularly to show fringes corresponding to 1.5 to 3Å lattice planes in crystals as resolution tests.

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