scholarly journals General Molecular Dynamics Approach to Understand the Mechanical Anisotropy of Monocrystalline Silicon under the Nanoscale Effects of Point Defect

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1965
Author(s):  
Wei Wan ◽  
Changxin Tang ◽  
Jianjie Zhang ◽  
Lang Zhou
Keyword(s):  
Molecular Dynamics ◽  
Point Defect ◽  
Mechanical Performance ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
Simulation Models ◽  
Monocrystalline Silicon ◽  
Mechanical Anisotropy ◽  
Extreme Stress ◽  
Fracture Anisotropy

Mechanical anisotropy and point defects would greatly affect the product quality while producing silicon wafers via diamond-wire cutting. For three major orientations concerned in wafer production, their mechanical performances under the nanoscale effects of a point defect were systematically investigated through molecular dynamics methods. The results indicated anisotropic mechanical performance with fracture phenomena in the uniaxial deformation process of monocrystalline silicon. Exponential reduction caused by the point defect has been demonstrated for some properties like yield strength and elastic strain energy release. Dislocation analysis suggested that the slip of dislocations appeared and created hexagonal diamond structures with stacking faults in the [100] orientation. Meanwhile, no dislocation was observed in [110] and [111] orientations. Visualization of atomic stress proved that the extreme stress regions of the simulation models exhibited different geometric and numerical characteristics due to the mechanical anisotropy. Moreover, the regional evolution of stress concentration and crystal fracture were interrelated and mutually promoted. This article contributes to the research towards the mechanical and fracture anisotropy of monocrystalline silicon.

scholarly journals The Size Effects of Point Defect on the Mechanical Properties of Monocrystalline Silicon: A Molecular Dynamics Study

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3011
Author(s):  
Wei Wan ◽  
Changxin Tang ◽  
An Qiu ◽  
Yongkang Xiang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Yield Strength ◽  
Point Defect ◽  
Size Effects ◽  
Constant Strain Rate ◽  
Monocrystalline Silicon ◽  
Dislocation Slip ◽  
Actual Strength ◽  
Yield Strength Variation

The molecular dynamics method was used to simulate the fracture process of monocrystalline silicon with different sizes of point defect under a constant strain rate. The mechanism of the defect size on the mechanical properties of monocrystalline silicon was also investigated. The results suggested that the point defect significantly reduces the yield strength of monocrystalline silicon. The relationships between the yield strength variation and the size of point defect fitted an exponential function. By statistically analyzing the internal stress in monocrystalline silicon, it was found that the stress concentration induced by the point defect led to the decrease in the yield strength. A comparison between the theoretical strength given by the four theories of strength and actual strength proved that the Mises theory was the best theory of strength to describe the yield strength of monocrystalline silicon. The dynamic evolution process of Mises stress and dislocation showed that the fracture was caused by the concentration effect of Mises stress and dislocation slip. Finally, the fractured microstructures were similar to a kind of two-dimensional grid which distributed along the cleavage planes while visualizing the specimens. The results of this article provide a reference for evaluating the size effects of point defects on the mechanical properties of monocrystalline silicon.

Displacement cascade evolution in tungsten with pre-existing helium and hydrogen clusters: a molecular dynamics study

2020 ◽  
Vol 111 (8) ◽  
pp. 698-705
Author(s):  
Mohammad Abu-Shams ◽  
Jeffery Moran ◽  
Ishraq Shabib
Keyword(s):  
Molecular Dynamics ◽  
Point Defect ◽  
Radiation Damage ◽  
Point Defects ◽  
High Energy ◽  
Dynamics Simulation ◽  
Power Relationship ◽  
Hydrogen Clusters ◽  
Displacement Cascades ◽  
Hydrogen Defects

Abstract The effects of radiation damage on bcc tungsten with preexisting helium and hydrogen clusters have been investigated in a high-energy environment via a comprehensive molecular dynamics simulation study. This research determines the interactions of displacement cascades with helium and hydrogen clusters integrated into a tungsten crystal generating point defect statistics. Helium or hydrogen clusters of atoms~0.1% of the total number of atoms have been randomly distributed within the simulation model and primary knock-on-atom (PKA) energies of 2.5, 5, 7.5 and 10 keV have been used to generate displacement cascades. The simulations quantify the extent of radiation damage during a simulated irradiation cycle using the Wigner-Seitz point defect identification technique. The generated point defects in crystals with and without pre-existing helium/hydrogen defects exhibit a power relationship with applied PKA energy. The point defects are classified by their atom type, defect type, and distribution within the irradiated model. The presence of pre-existing helium and hydrogen clusters significantly increases the defects (5 - 15 times versus pure tungsten models). The vacancy composition is primarily tungsten (e. g., ~70% at 2.5 keV) in models with pre-existing helium, but the interstitials are primarily He (e. g., ~89% at 10 keV). On the other hand, models with pre-existing hydrogen have a vacancy composition that is primarily tungsten (more than 90% irrespective of PKA energy), and the interstitial composition is more balanced between tungsten (average 46%) and hydrogen (average 54%) interstitials across the PKA range. The distribution of the atoms reveals that the tungsten point defects prefer to reside close to the position of cascade initiation, but helium or hydrogen defects reside close to the positions where clusters are built.

Experimental study of the dynamically induced rockburst of a rock wall with double free faces

2018 ◽  
Vol 28 (4) ◽  
pp. 611-637 ◽  
Author(s):  
Guoshao Su ◽  
Zhiyong Chen ◽  
J Woody Ju ◽  
Bin Zhao ◽  
Sizhou Yan ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Dynamic Loading ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
The Self ◽  
Rockburst Hazard ◽  
Dynamic Disturbance ◽  
Rock Wall ◽  
Free Face ◽  
Rock Structure

Dynamic disturbance is regarded as one of the most significant factors that induce rockburst around the boundary of underground excavation, particularly in high confining pressure conditions. In the present study, three types of dynamic loading tests are conducted to investigate the dynamically triggered rockburst behavior of a rock wall with double free faces. The three types of dynamic loading considered are the large stress single-pulse loading (mild-disturbance), the middle stress low-frequency cyclic loading (modest-disturbance), and the small stress high-frequency cyclic loading (weak-disturbance). The experimental results are analyzed and the damage evolution process during the dynamic disturbances is described. The tests reveal that the failure strain (i.e., the strain at unstable failure) of the dynamically triggered rockburst is greater than that of the self-initiated rockburst. The intensity of rockburst depends not only on the initial static stress level but also on the dynamic disturbance type. The rockburst induced by the mild-disturbance is mainly related to large amounts of disturbance energy imported. The rockburst caused by the modest-disturbance is contributed by the disturbance degradation of ultimate energy-storage capacity of specimen. The rockburst in a weak-disturbance specimen is primarily due to the disturbance aggravation of the damage in specimen and the elastic strain energy release. In particular, the rockburst hazard from the double free faces is more likely to be triggered and its result more serious than that of the rock structure with only one free face because the increasing free face decreases the rock strength. The fragmentation of the dynamically induced rockburst is larger than that of the self-initiated rockburst. With increasing time of dynamic loading, the damage induced by the modest-disturbance and the weak-disturbance first increases continually, subsequently increases steadily, and finally increases drastically. By contrast, the damage of the specimen under the mild-disturbance condition has a linearly increasing trend.

scholarly journals Molecular Dynamics Simulation of the Crystal Orientation and Temperature Influences in the Hardness on Monocrystalline Silicon

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Hongwei Zhao ◽  
Peng Zhang ◽  
Chengli Shi ◽  
Chuang Liu ◽  
Lei Han ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Crystal Orientation ◽  
Morse Potential ◽  
Amorphous Structure ◽  
Monocrystalline Silicon ◽  
Dynamics Simulation ◽  
Crystal Surfaces ◽  
Diamond Indenter ◽  
Cubic Structure ◽  
Simulation Results

A nanoindentation simulation using molecular dynamic (MD) method was carried out to investigate the hardness behavior of monocrystalline silicon with a spherical diamond indenter. In this study, Tersoff potential was used to model the interaction of silicon atoms in the specimen, and Morse potential was used to model the interaction between silicon atoms in the specimen and carbon atoms in the indenter. Simulation results indicate that the silicon in the indentation zone undergoes phase transformation from diamond cubic structure to body-centred tetragonal and amorphous structure upon loading of the diamond indenter. After the unloading of the indenter, the crystal lattice reconstructs, and the indented surface with a residual dimple forms due to unrecoverable plastic deformation. Comparison of the hardness of three different crystal surfaces of monocrystalline silicon shows that the (0 0 1) surface behaves the hardest, and the (1 1 1) surface behaves the softest. As for the influence of the indentation temperature, simulation results show that the silicon material softens and adhesiveness of silicon increases at higher indentation temperatures.

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