Atomic Scale Simulation of Cross Slip and Screw Dislocation Dipole Annihilation

1998 ◽  
Vol 538 ◽  
Author(s):  
Torben Rasmussen
Keyword(s):  
Screw Dislocation ◽  
Energy Barrier ◽  
Minimum Energy ◽  
Experimental Studies ◽  
Cross Slip ◽  
Atomic Scale ◽  
Atomistic Simulations ◽  
Minimum Energy Path ◽  
Dislocation Dipole ◽  
Single Screw

AbstractAtomistic simulations are used to study cross slip of a single screw dislocation as well as screw dislocation dipole annihilation in Cu. A configuration space path techniquex is applied to determine, without presumptions about the saddle point, the minimum energy path of transition for cross slip. The cross slip process is that proposed by Friedel and Escaig, and the energy of the in-plane constriction initiating cross slip is determined. A minimum stable dipole height much smaller than previously inferred from experimental studies is found. Relaxed screw dislocation dipoles adopt a skew configuration due to the anisotropy of Cu. The path technique is applied to investigate annihilation of stable screw dislocation dipoles, and the energy barrier for annihilation as a function of dipole height is determined for both homogeneous and heterogeneous cross slip leading to the annihilation. The results might be used as quantitative input into meso-/macro-scopical modelling approaches which rely on parameters deduced from either simulation or experiment.

Atomic-Scale Modeling of the Annihilation of Jogged Screw Dislocation Dipoles

1999 ◽  
Vol 578 ◽  
Author(s):  
T. Vegge ◽  
O. B. Pedersen ◽  
T. Leffers ◽  
K. W. Jacobsen
Keyword(s):  
Molecular Dynamics ◽  
Screw Dislocation ◽  
Atomic Scale ◽  
Atomistic Simulations ◽  
Elastic Band ◽  
Screw Dislocations ◽  
Scale Modeling ◽  
Band Method

AbstractUsing atomistic simulations we investigate the annihilation of screw dislocation dipoles in Cu. In particular we determine the influence of jogs on the annihilation barrier for screw dislocation dipoles. The simulations involve energy minimizations, molecular dynamics, and the Nudged Elastic Band method. We find that jogs on screw dislocations substantially reduce the annihilation barrier, hence leading to an increase in the minimum stable dipole height.

Nudged elastic band method and density functional theory calculation for finding a local minimum energy pathway of p-benzoquinone and phenol fragmentation in mass spectrometry

2017 ◽  
Vol 23 (1) ◽  
pp. 40-44 ◽  
Author(s):  
Natsuhiko Sugimura ◽  
Yoko Igarashi ◽  
Reiko Aoyama ◽  
Toshimichi Shibue
Keyword(s):  
Mass Spectrometry ◽  
Energy Barrier ◽  
Minimum Energy ◽  
Minimum Energy Path ◽  
Intermediate Structure ◽  
Elastic Band ◽  
Final State ◽  
Fragmentation Pathways ◽  
Reaction Coordinates ◽  
Band Method

Analysis of the fragmentation pathways of molecules in mass spectrometry gives a fundamental insight into gas-phase ion chemistry. However, the conventional intrinsic reaction coordinates method requires knowledge of the transition states of ion structures in the fragmentation pathways. Herein, we use the nudged elastic band method, using only the initial and final state ion structures in the fragmentation pathways, and report the advantages and limitations of the method. We found a minimum energy path of p-benzoquinone ion fragmentation with two saddle points and one intermediate structure. The primary energy barrier, which corresponded to the cleavage of the C–C bond adjacent to the CO group, was calculated to be 1.50 eV. An additional energy barrier, which corresponded to the cleavage of the CO group, was calculated to be 0.68 eV. We also found an energy barrier of 3.00 eV, which was the rate determining step of the keto-enol tautomerization in CO elimination from the molecular ion of phenol. The nudged elastic band method allowed the determination of a minimum energy path using only the initial and final state ion structures in the fragmentation pathways, and it provided faster than the conventional intrinsic reaction coordinates method. In addition, this method was found to be effective in the analysis of the charge structures of the molecules during the fragmentation in mass spectrometry.

Screw dislocation cross slip at cross-slip plane jogs and screw dipole annihilation in FCC Cu and Ni investigated via atomistic simulations

2015 ◽  
Vol 101 ◽  
pp. 10-15 ◽  
Author(s):  
S.I. Rao ◽  
D.M. Dimiduk ◽  
J.A. El-Awady ◽  
T.A. Parthasarathy ◽  
M.D. Uchic ◽  
...  
Keyword(s):  
Screw Dislocation ◽  
Slip Plane ◽  
Cross Slip ◽  
Atomistic Simulations

PHYSISORPTION TO CHEMISORPTION TRANSFORMATION OF A H2 MOLECULE ON B-DOPED FULLERENE C59B

2011 ◽  
Vol 10 (06) ◽  
pp. 839-847 ◽  
Author(s):  
CHUANJIN TIAN ◽  
WENYAN ZHAO ◽  
ZHIGANG WANG ◽  
MINGXING JIN
Keyword(s):  
Transition State ◽  
Energy Barrier ◽  
Minimum Energy ◽  
Transformation Process ◽  
Minimum Energy Path ◽  
First Principle ◽  
Adsorption State ◽  
First Principle Calculations ◽  
Dynamics Stability ◽  
H2 Molecule

By first principle calculations we have explored the minimum energy path of H2 molecule dissociating on the C59B which is a system as stable as C60 . Our results show that the transformation process from physisorption state (also called nondissociation adsorption state) to the chemisorption state of the H2 molecule on the C59B surface should cross a transition state. However, the energy barrier of this reaction is very low. Therefore, the dynamics stability of the physisorption state is not high.

A New Defect in Polyethylene Single Crystals

1973 ◽  
Vol 31 ◽  
pp. 70-71
Author(s):  
E. L. Thomas ◽  
S. L. Sass
Keyword(s):  
Single Crystals ◽  
Screw Dislocation ◽  
Small Distance ◽  
Dipole Model ◽  
Dislocation Dipole ◽  
Chain Folding ◽  
Black And White ◽  
Polymer Crystal ◽  
Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

scholarly journals Dynamic lattice distortions driven by surface trapping in semiconductor nanocrystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Burak Guzelturk ◽  
Benjamin L. Cotts ◽  
Dipti Jasrasaria ◽  
John P. Philbin ◽  
David A. Hanifi ◽  
...  
Keyword(s):  
Photon Energy ◽  
Semiconductor Nanocrystals ◽  
Atomic Scale ◽  
Atomistic Simulations ◽  
Shell System ◽  
Structural Distortions ◽  
Colloidal Semiconductor Nanocrystals ◽  
Femtosecond Electron Diffraction ◽  
Structural Deformations ◽  
Nonradiative Processes

AbstractNonradiative processes limit optoelectronic functionality of nanocrystals and curb their device performance. Nevertheless, the dynamic structural origins of nonradiative relaxations in such materials are not understood. Here, femtosecond electron diffraction measurements corroborated by atomistic simulations uncover transient lattice deformations accompanying radiationless electronic processes in colloidal semiconductor nanocrystals. Investigation of the excitation energy dependence in a core/shell system shows that hot carriers created by a photon energy considerably larger than the bandgap induce structural distortions at nanocrystal surfaces on few picosecond timescales associated with the localization of trapped holes. On the other hand, carriers created by a photon energy close to the bandgap of the core in the same system result in transient lattice heating that occurs on a much longer 200 picosecond timescale, dominated by an Auger heating mechanism. Elucidation of the structural deformations associated with the surface trapping of hot holes provides atomic-scale insights into the mechanisms deteriorating optoelectronic performance and a pathway towards minimizing these losses in nanocrystal devices.

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