Computational Diagnostics for Detecting Phase Transitions During Nanoindentation

1992 ◽  
Vol 291 ◽  
Author(s):  
Susanne M. Lee ◽  
Carol G. Hoover ◽  
Jeffrey S. Kallman ◽  
William G. Hoover ◽  
Anthony J. De Groot ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Phase Transitions ◽  
Yield Strength ◽  
Amorphous Silicon ◽  
Diagnostic Tool ◽  
Structural Changes ◽  
Nonequilibrium Molecular Dynamics ◽  
Simulation Results ◽  
Diffraction Patterns ◽  
Dynamics Simulations

ABSTRACTWe study nanoindentation of silicon using nonequilibrium molecular dynamics simulations with up to a million particles. Both crystalline and amorphous silicon samples are considered. We use computational diffraction patterns as a diagnostic tool for detecting phase transitions resulting from structural changes. Simulations of crystalline samples show a transition to the amorphous phase in a region a few atomic layers thick surrounding the lateral faces of the indentor, as has been suggested by experimental results. Our simulation results provide estimates for the yield strength (nanohardness) of silicon for a range of temperatures.

scholarly journals Calculation of Diffraction Patterns Associated with Electron Irradiation Induced Amorphization of CuTi.

1990 ◽  
Vol 209 ◽  
Author(s):  
R. Devanathan ◽  
N. Q. Lam ◽  
M. J. Sabochick ◽  
P. Okamoto ◽  
M. Meshii
Keyword(s):  
Molecular Dynamics ◽  
Correlation Function ◽  
Electron Irradiation ◽  
Pair Correlation Function ◽  
Structural Changes ◽  
Pair Correlation ◽  
Long Range Order ◽  
New Approach ◽  
Diffraction Patterns ◽  
Dynamics Simulations

ABSTRACTA new approach that uses the multislice method in conjunction with molecular dynamics simulations to study electron irradiation induced amorphisation is presented. Diffraction patterns were calculated for CuTi and found to be more sensitive than the pair correlation function to the structural changes preceding amorphisation. The results from this approach and from a study of long range order are presented.

scholarly journals Nonequilibrium Molecular Dynamics Simulations of Coal Ash

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 11
Author(s):  
Shi Yu ◽  
Ruizhi Chu ◽  
Xiao Li ◽  
Guoguang Wu ◽  
Xianliang Meng
Keyword(s):  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Einstein Equation ◽  
Md Simulation ◽  
Coal Ash ◽  
Nonequilibrium Molecular Dynamics ◽  
Strong Temperature Dependence ◽  
Coal Ashes ◽  
Simulation Results ◽  
Dynamics Simulations

Both molecular dynamics (MD) and nonequilibrium molecular dynamics (NEMD) simulations were performed to simulate coal ashes using the Guillot-Sator model in this work. The structural and transport properties of coal ashes at high temperatures have been obtained. Superheating of coal ash system with anorthite crystal structure initial configuration has been observed for MD simulation which explains the discrepancy between previous MD simulation results and FactSage thermochemical calculations. The fluxing effects of both calcium oxide and sodium oxide have been investigated systematically through MD and NEMD simulations. Moreover, the viscosities of coal ash systems have been computed by two methods: (1) Stokes-Einstein equation; (2) NEMD simulations. Estimations of viscosities for various coal ash systems based on Stokes-Einstein equation exhibit a strong temperature dependence of viscosity, which agrees with previous experimental results. On the other hand, NEMD simulation results that showed a strong shear-thinning feature, failed to reproduce this strong temperature dependence of viscosity, possibly due to the short simulation time. Nevertheless, NEMD simulations not only provide us detailed information about atoms dynamics under shear, but also allow us to model the coal ash system far from equilibrium which cannot be accessed by thermodynamics calculation using software like FactSage.

ATOMISTIC SIMULATION OF LASER ABLATION OF DIAMOND AND SILICON (111) SURFACE

1999 ◽  
Vol 06 (06) ◽  
pp. 1025-1030 ◽  
Author(s):  
C. Z. WANG ◽  
K. M. HO
Keyword(s):  
Molecular Dynamics ◽  
Laser Ablation ◽  
Lattice Dynamics ◽  
Atomistic Simulation ◽  
Structural Changes ◽  
Tight Binding ◽  
Femtosecond Laser Ablation ◽  
Ultrafast Laser ◽  
Simulation Results ◽  
Dynamics Simulations

Tight-binding molecular dynamics simulations are performed to study femtosecond-laser ablation of diamond and silicon (111) surface. The simulation results show that under intense ultrafast laser ablation the diamond (111) surface graphitizes while the silicon (111) surface melts spontaneously. All structural changes occur within a few hundred femtoseconds, which is much shorter than the typical lattice dynamics time scale, in consistent with experimental observations.

scholarly journals CO2 and SO2 Pressure-Driven Adsorption by 3D Graphene Nanoslits: A Molecular Dynamics Study

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Amanda Caroline Borges ◽  
Mateus H. Köhler ◽  
José Rafael Bordin
Keyword(s):  
Molecular Dynamics ◽  
Membrane Properties ◽  
Nonequilibrium Molecular Dynamics ◽  
Anthropogenic Effect ◽  
Bulk State ◽  
3D Graphene ◽  
Gas Molecules ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Pollutant Gases

Nonequilibrium molecular dynamics simulations are employed to study the adsorption and blockage properties of a 3D graphene membrane. Specifically, we are interested in the mixtures of carbon dioxide (CO2) and sulfur dioxide (SO2), two of the most relevant pollutant gases for the anthropogenic effect in global warming. We simulate cases with distinct proportion of gases in the mixture. Our results indicate that the 3D graphene slit is able to absorb 90% or more of the gas molecules. We show that this property came from the fact that both CO2 and SO2 molecules are attracted by the graphene pore, which compensates for the entropic barrier that exists when leaving the bulk state to the confined state. Also, the simulation results show that changing the interlayer separation between the graphene sheets is possible in order to change the membrane properties, from absorbent to blockage. These results help to understand the properties of 3D graphene nanoslits and their application as highly selective filters.

scholarly journals Fluctuation Relations for Dissipative Systems in Constant External Magnetic Field: Theory and Molecular Dynamics Simulations

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 146
Author(s):  
Alessandro Coretti ◽  
Lamberto Rondoni ◽  
Sara Bonella
Keyword(s):  
Magnetic Field ◽  
Molecular Dynamics ◽  
External Magnetic Field ◽  
Molecular Dynamics Simulations ◽  
Nonequilibrium Molecular Dynamics ◽  
Dissipative Systems ◽  
Common Belief ◽  
Fluctuation Relations ◽  
Dynamics Simulations ◽  
Constant External Magnetic Field

We illustrate how, contrary to common belief, transient Fluctuation Relations (FRs) for systems in constant external magnetic field hold without the inversion of the field. Building on previous work providing generalized time-reversal symmetries for systems in parallel external magnetic and electric fields, we observe that the standard proof of these important nonequilibrium properties can be fully reinstated in the presence of net dissipation. This generalizes recent results for the FRs in orthogonal fields—an interesting but less commonly investigated geometry—and enables direct comparison with existing literature. We also present for the first time a numerical demonstration of the validity of the transient FRs with nonzero magnetic field via nonequilibrium molecular dynamics simulations of a realistic model of liquid NaCl.

Computer-Generated Structural Models for a-Si:H

1988 ◽  
Vol 141 ◽  
Author(s):  
Laurent J. Lewis ◽  
Normand Mousseau ◽  
FranÇois Drolet
Keyword(s):  
Molecular Dynamics ◽  
Boundary Conditions ◽  
Amorphous Silicon ◽  
Periodic Boundary ◽  
Hydrogenated Amorphous Silicon ◽  
Structural Models ◽  
Periodic Boundary Conditions ◽  
Dynamics Simulations ◽  
Hydrogenated Amorphous ◽  
Good Agreement

AbstractA new algorithm for generating fully-coordinated hydrogenated amorphous silicon models with periodic boundary conditions is presented. The hydrogen is incorporated into an a-Si matrix by a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, making sure that four-fold coordination is preserved and that no rings with less than 5 members are created. After each addition of hydrogen, the structure is fully relaxed. The models so obtained, to be used as input to molecular dynamics simulations, are found to be in good agreement with experiment. A model with 12 at.% H is discussed in detail.

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