ATOMISTIC VIEWS OF DYNAMICAL FRACTURE INSTABILITIES IN SILICON: MOLECULAR DYNAMICS STUDIES

2013 ◽  
Vol 27 (24) ◽  
pp. 1350171
Author(s):  
P. GUO ◽  
Y. W. LUO ◽  
M. LI ◽  
P. F. YUAN ◽  
Q. SUN ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Crack Tip ◽  
Tensile Load ◽  
Uniaxial Tensile ◽  
Fracture Plane ◽  
Crack Plane ◽  
Load Mode ◽  
Simulation Results ◽  
Atomic Ring ◽  
Dynamics Simulations

This study investigates the crystallographic orientations most widely known to exhibit fractures in silicon, such as those on the (111) plane cracks travelling along the [Formula: see text] direction ([Formula: see text] cracks). The (111) crack plane is believed to be the most stable fracture plane. However, fracture instabilities caused by brittle crack jumps remain on (111) the crack plane in a discontinuous manner. In this study, molecular dynamics simulations were performed to investigate the atomistic-level studies of fracture properties under a uniaxial tensile load (mode I load) in the (111) [Formula: see text] Si system. Our simulation results suggest that the formation of untypical-membered Si atomic rings in the vicinity of the crack tip, which can be induced by atomic stress near the crack tip, has an important role in the behavior of crack propagation instabilities. The presence of untypical-membered Si atomic rings acts as a self-protecting mechanism that contribute in maintaining the crack on the (111) fracture plane. Notably, our simulations also presented that the situation when a seven- Si atomic ring moves away from the crack tip associated with a sudden jump of crack speed can be regarded as the origin of the peculiar speed advancement behavior of the [Formula: see text] systems. Moreover, several of our simulation results are in agreement with related experimental measurements.

Molecular Dynamics of Crack Growth in Nickel and Nickel-Aluminum Bi-Metallic Interface System Under Cyclic Loading

2011 ◽  
Author(s):  
Yojna Purohit ◽  
Ram Mohan
Keyword(s):  
Molecular Dynamics ◽  
Cyclic Loading ◽  
Crack Propagation ◽  
Crack Growth ◽  
Void Nucleation ◽  
Crack Tip ◽  
Propagation Mechanism ◽  
Crack Plane ◽  
Embedded Atom ◽  
Dynamics Simulations

Molecular dynamics simulations using embedded atom method inter-atomic potential were used to study crack propagation under cyclic loading in a Ni single crystal and a Ni-Al bi-metallic system. The crack in Ni-Al initiates and propagates from Ni towards the Ni-Al interface. The cyclic loading was applied in a strain controlled manner with constant amplitude of maximum strains (emax) applied to the two systems. The crack growth and propagation mechanism of a crack propagating in Ni were compared with the crack growth and propagation of a surface crack in Ni-Al at two different values of emax. Our results suggest that depending on the maximum value of the applied strain (emax), the crack propagates either by fatigue cleavage of the atomic bonds in the crack plane or by void nucleation in the regions near the crack tip. The creation of voids slows down crack growth in both the Ni and Ni-Al at higher value of emax. A comparison of crack growth under tensile and cyclic loading (emax, 0.046) suggest that plastic deformation around crack tip dominate crack propagation during tensile loading that result in slower crack growth (due to early nucleation of dislocations at the crack tip), when compared to crack growth under cyclic loading.

Molecular Dynamics Simulations on the Chain Fold During the Isothermal Orientation of n-Alkanes on Graphene

2021 ◽  
Author(s):  
Zhi Meng Zhang ◽  
Hua Yang ◽  
Jun Xia Shi ◽  
Jia Jun Wang ◽  
Zheng Guo Huang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Orientation ◽  
Dynamics Simulation ◽  
Ordered Structure ◽  
Graphene Surface ◽  
Parallel Orientation ◽  
Chain Folding ◽  
Hydrocarbon Chains ◽  
Simulation Results ◽  
Dynamics Simulations

Abstract The orientation of hydrocarbon chains plays a key role in the applications of organic materials. And chain folding in the process of molecular orientation is also of great significance for the design of organic molecular thin films. The effect of chain length and simulation temperature on the isothermal orientation of n-alkanes on graphene surface is studied by molecular dynamics simulation in this paper. And the chain folding is also described. The n-alkanes can form perpendicular ordered structure, parallel ordered structure or perpendicular orientation at relative low temperature and parallel orientation at relative high temperature on graphene surface. The chain fold happens when long n-alkanes form perpendicular ordered structure on graphene surface. And the simulation results show the interactions of n-alkane−graphene and n-alkane−n-alkane affect chain fold.

Molecular Dynamics Simulations of Nanocomposite Diamond-Like Carbon

2005 ◽  
Author(s):  
G. T. Gao ◽  
J. D. Schall ◽  
K. Van Workum ◽  
P. T. Mikulski ◽  
J. A. Harrison
Keyword(s):  
Molecular Dynamics ◽  
Elastic Constants ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Diamond Structure ◽  
The Core ◽  
Constant Tension ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Carbon Network

A constant tension and constant temperature molecular dynamics simulation method was used in the calculations of the elastic constants of the nanocomposite systems. The nanocomposite systems contain a core of sp3 diamond structure surrounded by an amorphous carbon network. The simulation results show that the elastic properties of nanocomposites of diamond-like carbons are closely related to the size of the sp3 diamond core; the bigger the core, the larger the elastic constants, and the system becomes more anisotropic.

Self-Assembly of Graphene Nanoribbons with Unsaturated Edges

2012 ◽  
Vol 1407 ◽  
Author(s):  
Andrew L. J. Pang ◽  
Viacheslav Sorkin ◽  
Yong-Wei Zhang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Self Assembly ◽  
Bond Order ◽  
Graphene Nanoribbons ◽  
The Self ◽  
Graphene Nanoscrolls ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Stable Structures

ABSTRACTWe studied the self-assembly mechanisms of Graphene Nanoribbon (GNR) with unsaturated edges and demonstrated the ability of GNR to self-assemble into novel stable structures. We proposed three mechanisms which dictate the self-assembly evolution of GNR with unsaturated edges. Using the Adaptive Intermolecular Reactive Empirical Bond-Order (AIREBO) potential, we performed molecular dynamics simulations on initially-planar GNRs with unsaturated edges. The simulation results showed that the self-assembly mechanisms and final conformations of the GNRs correlate well with the proposed GNR self-assembly mechanisms. Furthermore, the simulations also showed the ability of a narrow GNR to self-assemble into various nanostructures, such as tapered graphene nano-rings and graphene nanoscrolls with an embedded nanotube.

scholarly journals Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Xin Mu ◽  
Lili Wang ◽  
Xueming Yang ◽  
Pu Zhang ◽  
Albert C. To ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Germanium ◽  
Phonon Scattering ◽  
Low Thermal Conductivity ◽  
Structural Hierarchy ◽  
Si Nanowire ◽  
Hierarchical Structuring ◽  
Simulation Results ◽  
Dynamics Simulations

Abstract Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

scholarly journals Surface Energy-Controlled Self-Collapse of Carbon Nanotube Bundles With Large and Reversible Volumetric Deformation

2013 ◽  
Vol 80 (4) ◽  
Author(s):  
Yuan Cheng ◽  
Nicola Maria Pugno ◽  
Xinghua Shi ◽  
Bin Chen ◽  
Huajian Gao
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Surface Energy ◽  
Nanotube Bundles ◽  
Volumetric Deformation ◽  
Equilibrium Configurations ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Effect Of Surface

Molecular dynamics simulations are performed to investigate the effect of surface energy on equilibrium configurations and self-collapse of carbon nanotube bundles. It is shown that large and reversible volumetric deformation of such bundles can be achieved by tuning the surface energy of the system through an applied electric field. The dependence of the bundle volume on surface energy, bundle radius, and nanotube radius is discussed via a dimensional analysis and determined quantitatively using the simulation results. The study demonstrates potential of carbon nanotubes for applications in nanodevices where large, reversible, and controllable volumetric deformations are desired.

Atomistic Simulation of Deformation Behavior at a Crack Tip in Magnesium Single Crystal

2011 ◽  
Vol 675-677 ◽  
pp. 949-951
Author(s):  
Li Ming Jiang ◽  
Ya Fang Guo
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Deformation Behavior ◽  
Atomistic Simulation ◽  
Shear Banding ◽  
Crack Tip ◽  
Temperature Deformation ◽  
Dynamics Simulations ◽  
Main Deformation ◽  
Model Crack

The mechanisms of low-temperature deformation around a crack tip in a hexagonally closed-packed (hcp) magnesium single crystal have been studied by molecular dynamics simulations. In our simulation a {1010} < 12 10 > model I (opening model) crack is selected. The results indicate that slip on the basal plane is activated due to the shear stress at the crack tip. Thus shear banding caused by a successive slip of the basal planes is the main deformation way for this type of crack.

scholarly journals Lanthanum Influence onEuAlO3Perovskite Structural Properties: Experimental and Molecular Dynamics Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Enrique Lima ◽  
María Elena Villafuerte-Castrejón ◽  
José Saniger ◽  
Victor Lara ◽  
Jorge E. Sánchez-Sánchez ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Structural Properties ◽  
Mas Nmr ◽  
Ftir Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lanthanum Ions ◽  
Simulation Results ◽  
Dynamics Simulations

X-ray diffraction,27Al MAS NMR, and FTIR spectra along with results of molecular dynamics simulations were used to characterise LaxEu1−xAlO3perovskites forx=0.3,  0.1. Experimental and simulation results show that local changes in the perovskite-like structure can be achieved as lanthanum ions substitute europium ones. The introduction of La3+ions in the EuAlO3parent causes an increase in the mobility of oxygen network.

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