scholarly journals Molecular Dynamics Study on Lubrication Mechanism in Crystalline Structure between Copper and Sulfur

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Ken-ichi Saitoh ◽  
Tomohiro Sato ◽  
Masanori Takuma ◽  
Yoshimasa Takahashi ◽  
Ryuketsu Chin
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Potential Function ◽  
Crystalline Structure ◽  
Interatomic Potential ◽  
Hexagonal Phase ◽  
Interatomic Interaction ◽  
Md Simulations ◽  
Shear Loading ◽  
Atomistic Modeling

To clarify the nanosized mechanism of good lubrication in copper disulfide (Cu2S) crystal which is used as a sliding material, atomistic modeling of Cu2S is conducted and molecular dynamics (MD) simulations are performed in this paper. The interatomic interaction between atoms and crystalline structure in the phase of hexagonal crystal of Cu2S are carefully estimated by first-principle calculations. Then, approximating these interactions, we originally construct a conventional interatomic potential function of Cu2S crystal in its hexagonal phase. By using this potential function, we perform MD simulation of Cu2S crystal which is subjected to shear loading parallel to the basal plane. We compare results obtained by different conditions of sliding directions. Unlike ordinary hexagonal metallic crystals, it is found that the easy-glide direction does not always show small shear stress for Cu2S crystal. Besides, it is found that shearing velocity affects largely the magnitude of averaged shear stress. Generally speaking, higher velocity results in higher resistance against shear deformation. As a result, it is understood that Cu2S crystal exhibits somewhat liquid-like (amorphous) behavior in sliding condition and shear resistance increases with increase of sliding speed.

Molecular Dynamics Simulations of Diffusion of O2 and N2 Penetrants in Polydimethylsiloxane-Based Nanocomposites

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Douglas E. Spearot ◽  
Alex Sudibjo ◽  
Varun Ullal ◽  
Adam Huang
Keyword(s):  
Molecular Dynamics ◽  
Polymer Composites ◽  
Diffusion Coefficients ◽  
Metal Particle ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Coarse Grained ◽  
Cu Nanoparticles ◽  
Cu Nanoparticle ◽  
Nanoparticle Inclusions

Recently, metal particle polymer composites have been proposed as sensing materials for micro corrosion sensors. To design the sensors, a detailed understanding of diffusion through metal particle polymer composites is necessary. Accordingly, in this work molecular dynamics (MD) simulations are used to study the diffusion of O2 and N2 penetrants in metal particle polymer nanocomposites composed of an uncross-linked polydimethylsiloxane (PDMS) matrix with Cu nanoparticle inclusions. PDMS is modeled using a hybrid interatomic potential with explicit treatment of Si and O atoms along the chain backbone and coarse-grained methyl side groups. In most models examined in this work, MD simulations show that diffusion coefficients of O2 and N2 molecules in PDMS-based nanocomposites are lower than that in pure PDMS. Nanoparticle inclusions act primarily as geometric obstacles for the diffusion of atmospheric penetrants, reducing the available porosity necessary for diffusion, with instances of O2 and N2 molecule trapping also observed at or near the PDMS/Cu nanoparticle interfaces. In models with the smallest gap between Cu nanoparticles, MD simulations show that O2 and N2 diffusion coefficients are higher than that in pure PDMS at the lowest temperatures studied. This is due to PDMS chain confinement at low temperatures in the presence of the Cu nanoparticles, which induces low-density regions within the PDMS matrix. MD simulations show that the role of temperature on diffusion can be modeled using the Williams–Landel–Ferry equation, with parameters influenced by nanoparticle content and spacing.

A molecular dynamics investigation on grain disappearance at a triple junction in polycrystalline silicon

2001 ◽  
Vol 677 ◽  
Author(s):  
Alessandra Satta ◽  
Luciano Colombo ◽  
Fabrizio Cleri
Keyword(s):  
Molecular Dynamics ◽  
Triple Junction ◽  
Polycrystalline Silicon ◽  
Critical Radius ◽  
Interatomic Potential ◽  
Atomistic Modeling ◽  
Triple Junctions ◽  
Atomistic Region ◽  
The Stability ◽  
Dynamics Simulations

ABSTRACTTopological changes in microstructure are strictly related to the microscopic evolution of triple junctions (TJ). The three-sided grain disappearance, usually called T2 process, is here investigated via 3D-atomistic modeling. In particular the stability of a three-sided grain insertion in a triple junction in silicon is studied within the framework of Molecular Dynamics simulations. The Stillinger-Weber interatomic potential is adopted and constant-traction border conditions are considered to ensure a proper embedding of the atomistic region in a virtually infinite bulk continuum. Dealing with the T2-event, the critical radius below which the three- sided inner grain become unstable is evaluated to be three to four times the lattice constant of silicon. Moreover, we show that the instability sets in through the amorphization of the central shrinking grain.

Physical properties of high-temperature solid alkali chlorides by molecular dynamics simulation using a recent EIM interatomic potential

2019 ◽  
Vol 33 (10) ◽  
pp. 1950088 ◽  
Author(s):  
Xiandai Cui ◽  
Jiaoqun Zhu ◽  
Hong Xu ◽  
Xiaomin Cheng ◽  
Weibing Zhou
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Experimental Values ◽  
Alkali Chlorides ◽  
Change Material

Thermophysical properties of phase change material NaCl and KCl were calculated using molecular dynamics (MD) simulations and a recent EIM interatomic potential. Density, thermal expansion coefficient, specific heat capacity were computed using equilibrium MD (EMD) simulations. The results are very close to the experimental values. The thermal conductivity was computed using two non-equilibrium MD (NEMD) methods and the results were compared with the experimental data. They appear to be relatively reasonable. Binary NaCl/KCl systems have also been investigated. The specific heat capacity with different compositions are calculated. They are very close with recent experimental results.

Molecular Dynamics Simulation of Nano-Sized Crystallization During Plastic Deformation in an Amorphous Metal

2000 ◽  
Vol 634 ◽  
Author(s):  
R. Tarumi ◽  
A. Ogura ◽  
M. Shimojo ◽  
K. Takashima ◽  
Y. Higo
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Shear Stress ◽  
Phase Transformation ◽  
Molecular Dynamics Simulation ◽  
Shear Strain ◽  
Orientation Relationship ◽  
Crystalline Structure ◽  
Amorphous Metal ◽  
Dynamics Simulation

ABSTRACTAn NTP ensemble molecular dynamics simulation was carried out to investigate the mechanism of nano-sized crystallization during plastic deformation in an amorphous metal. The atomic system used in this study was Ni single component. The total number of Ni atoms was 1372. The Morse type inter-atomic potential was employed. An amorphous model was prepared by a quenching process from the liquid state. Pure shear stresses were applied to the amorphous model at a temperature of 50 K. At applied stresses of less than 2.4GPa, a linear relation between shear stress and shear strain was observed. However, at an applied shear stress of 2.8 GPa, the amorphous model started to deform significantly until shear strain reached to 0.78. During this deformation process, phase transformation from amorphous into crystalline structure (fcc) was observed. Furthermore, an orientation relationship between shear directions and crystalline phase was obtained, that is, two shear directions are parallel to a (111) of the fcc structure. This crystallographic orientation relationship agreed well with our experimental result of Ni-P amorphous alloy. Mechanisms of phase transformation from amorphous into crystalline structure were discussed.

Atomistic study of chemical effect on local structure in Mg-based metallic glasses

RSC Advances ◽  
2015 ◽  
Vol 5 (58) ◽  
pp. 46861-46868
Author(s):  
Q. Wang ◽  
J. H. Li ◽  
J. B. Liu ◽  
B. X. Liu
Keyword(s):  
Molecular Dynamics ◽  
Metallic Glasses ◽  
Local Structure ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Chemical Effect ◽  
Chemical Effects ◽  
Atomistic Study

By applying a recently constructed interatomic potential, molecular dynamics (MD) simulations were performed to investigate the structural origin of chemical effects in Mg–Cu–Ni ternary metallic glasses.

A method for analyzing nanomechanical deformation of nanocrystalline Ni at higher timesteps than is possible in classical molecular dynamics

2006 ◽  
Vol 978 ◽  
Author(s):  
Vikas Tomar
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Strain Rate ◽  
Defect Formation ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Classical Molecular Dynamics ◽  
Rate Dependent ◽  
Nanocrystalline Structures ◽  
Defect Nucleation

AbstractA majority of computational mechanical analyses of nanocrystalline materials have been carried out using classical molecular dynamics (MD). Due to the fundamental reason that the MD simulations must resolve atomic level vibrations, they cannot be carried out at the timescale of the order of microseconds. Additionally, MD simulations have to be carried out at very high loading rates (∼108 s−1) rarely observed in experiments. In this investigation a modified Hybrid Monte Carlo (HMC) method that can be used to analyze time-dependent (strain rate dependent) atomistic mechanical deformation of nanocrystalline structures at higher timescales than currently possible using MD is established. In this method there is no restriction on the size of MD timestep except that it must be such that to ensure a reasonable acceptance rate between consecutive Monte-Carlo (MC) time-steps. For the purpose of comparison HMC analyses of a nanocrystalline Ni sample at a strain rate of 109 s−1 with three different timesteps, viz. 2 fs, 4fs, and 8 fs, are compared with the analyses based on MD simulations at the same strain rate and a MD timestep of 2 fs. MD simulations of nanocrystalline Ni reproduce the defect nucleation and propagation results as well as strength values reported in the literature. In addition, HMC with timestep of 8 fs correctly reproduces defect formation and stress-strain response observed in the case of MD simulations with permissible timestep of 2 fs (for the interatomic potential used 2 fs is the highest MD timestep). Simulation time analyses show that by using HMC a saving of the order of 4 can be achieved bringing the atomistic analyses closer to the continuum timescales.

Molecular Dynamics Simulation of Interaction between Screw Dislocation and Copper Precipitate in Iron

2008 ◽  
Vol 33-37 ◽  
pp. 895-900 ◽  
Author(s):  
Akiyuki Takahashi ◽  
Yuji Aoki ◽  
Masanori Kikuchi
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Molecular Dynamics Simulation ◽  
Screw Dislocation ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Peierls Stress ◽  
Attractive Interaction ◽  
Good Prediction ◽  
Critical Resolved Shear Stress

This paper provides the results of the MD simulations of the interaction between a screw dislocation and a copper precipitate in iron. From the results, the screw dislocation has an attractive interaction with the copper precipitate. Also, the dependence of the Critical Resolved Shear Stress (CRSS) for the screw dislocation to break away from the copper precipitate on the size of the precipitate and temperature is studied. Finally, the CRSS obtained by the MD simulations is modeled statistically using a Russel-Brown model. Then we found that an addition of the Peierls stress, which is calculated by the MD simulations, to the Russel-Brown model gives a good prediction of the CRSS.

scholarly journals Hybrid machine learning assisted quantification of the compound internal and external uncertainties of graphene: Towards inclusive analysis and design

2021 ◽  
Author(s):  
Kritesh K. Gupta ◽  
Tanmoy Mukhopadhyay ◽  
Lintu Roy ◽  
Sudip Dey
Keyword(s):  
Machine Learning ◽  
Molecular Dynamics ◽  
Interatomic Potential ◽  
Md Simulations ◽  
First Principle ◽  
Reliability Of Results ◽  
Analysis And Design ◽  
Hybrid Machine ◽  
Inclusive Analysis

Reliability of results derived from molecular dynamics (MD) simulations depends on the adopted interatomic potential (IP), which is mathematically fitted to the data obtained from first principle approaches or experiments....

Dynamical Structure Factor and Vibrational Normal Modes of SiO2 Glass

1992 ◽  
Vol 291 ◽  
Author(s):  
Wei Jin ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Molecular Dynamics ◽  
Structure Factor ◽  
Interatomic Potential ◽  
Inelastic Neutron Scattering ◽  
Normal Modes ◽  
Dynamic Structure ◽  
Md Simulations ◽  
Inelastic Neutron ◽  
Dynamical Structure ◽  
Dynamical Matrix

ABSTRACTWe study the atomic vibrational dynamics in silica glass (a-SiO2) using molecular-dynamics (MD) simulations and classical lattice dynamics method. The SiO2 glasses were generated by molecular-dynamics and steepest-descent quench (SDQ) using an effective interatomic potential consisting of two-body and three-body interactions. The frequency and eigenvectors of vibrational normal modes are obtained by diagonalization of the dynamical matrix. The partial and total vibrational density of states (DOS), bond-projected DOS, participation ratio (PR), and neutron-weighted dynamic structure factor are calculated. The results are compared with inelastic neutron scattering experiments on SiO2 glass.

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