scholarly journals Molecular Dynamics Studies of Surface Indentation in Two Dimensions

1990 ◽  
Vol 193 ◽  
Author(s):  
J. Belak ◽  
I. F. Stowers
Keyword(s):  
Molecular Dynamics ◽  
Two Dimensions ◽  
Metallic Surface ◽  
Spherical Ball ◽  
Elastic And Plastic Deformations ◽  
The Creation ◽  
Non Equilibrium Molecular Dynamics ◽  
Body Potential ◽  
Edge Dislocations ◽  
Embedding Function

ABSTRACTNon-equilibrium molecular dynamics is used to study the indentation of an ideal metallic surface by a hard spherical ball. The problem is symmetric about the axis of the ball and we choose to study the deformation in two dimensions. We use the simple embedding function F(ρ) = 2eρln ρ along with the Lennard-Jones two body potential to model a material resembling copper. We present a calculation of the st'ress field (from the internal atomistic description) for both elastic and plastic deformations. The material deforms plastically through the creation of edge dislocations and the flow of material around the sides of the indenter. The creation of dislocations is reversible—they return to the surface (anneal out) when the indenter is removed. The plastic flow leads to a permanent indentation in the surface.

Void and Dislocation Microstructure Development in Heteroepitaxial Film Growth

1995 ◽  
Vol 399 ◽  
Author(s):  
Richard W. Smith ◽  
David J. Srolovitz
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Film Growth ◽  
Lattice Misfit ◽  
Two Dimensional ◽  
Microstructure Development ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Film Substrate ◽  
Edge Dislocations

ABSTRACTTwo dimensional, non-equilibrium molecular dynamics simulations have been performed to examine the microstructures of both homoepitaxial and heteroepitaxial thin films grown on single crystal substrates. The principal microstructural features to develop within these films are small voids and edge dislocations. Voids form near the surface of the growing film as surface depressions between microcolumns pinch off to become closed volumes. These voids often form in such a way as to introduce dislocations into the crystal with their cores positioned within the voids. Dislocations are also formed during heteroepitaxy at the interface between the substrate and film. These dislocations tend to be mobile. When voids are present in the film and when the lattice misfit is low, dislocations tend to be trapped in the voids or pulled toward them due to dislocation image interactions. Once attached to voids, dislocations are effectively pinned there. When voids are absent or when the misfit is high, dislocations are restricted to the film-substrate interface. In the case of heteroepitaxy, dislocations are found to relieve either tensile or compressive misfit stresses. Misfit stresses may also be accommodated, to some extent, merely by the free volume of the voids themselves.

Creation and Motion of Edge Dislocations in Copper Single Crystals

1997 ◽  
Vol 505 ◽  
Author(s):  
Masaodoyama ◽  
Yoshiaki Kogure ◽  
Tadatoshi Nozaki
Keyword(s):  
Molecular Dynamics ◽  
Single Crystals ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Shockley Partial Dislocation ◽  
Shockley Partial ◽  
Small Crystals ◽  
The Creation ◽  
Copper Single Crystals ◽  
Edge Dislocations

ABSTRACTDislocations were created near the center of the surface (110) of copper small crystals whose surfaces are (111), (111), (110), (110), (112), and (112) by use of n-body atom potentials and molecular dynamics. At first, a Heidenreich-Shockley partial dislocation was created. As the partial dislocation proceeds, the partial dislocation and the surface was connected with a stacking fault until the next Heidenreich-Shockley partial dislocation was created at the surface.Just before the creation of a partial dislocation the stress was the highest. For larger crystals, forming a step on (110) plane was not enough and a shear was necessary to move dislocations.

A Molecular Dynamics Study of Thermal Conductivity in Nanocomposites via the Phonon Wave Packet Method

2009 ◽  
Author(s):  
Zhiting Tian ◽  
Sang Kim ◽  
Ying Sun ◽  
Bruce White
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Wave Packet ◽  
Molecular Dynamics Simulations ◽  
Phonon Scattering ◽  
Flow Direction ◽  
Normal Incidence ◽  
Material Interfaces ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

The phonon wave packet technique is used in conjunction with the molecular dynamics simulations to directly observe phonon scattering at material interfaces. The phonon transmission coefficient of nanocomposites is examined as a function of the defect size, thin film thickness, orientation of interface to the heat flow direction. To generalize the results based on phonons in a narrow frequency range and at normal incidence, the effective thermal conductivity of the same nanocomposite structure is calculated using non-equilibrium molecular dynamics simulations for model nanocomposites formed by two mass-mismatched Ar-like solids and heterogeneous Si-SiCO2 systems. The results are compared with the modified effective medium formulation for nanocomposites.

A Theoretical Study of the Temperature Gradient Effect on the Soret Coefficient in n-Pentane/n-Decane Mixtures Using Non-Equilibrium Molecular Dynamics

2020 ◽  
Vol 45 (4) ◽  
pp. 319-332
Author(s):  
Xiaoyu Chen ◽  
Ruquan Liang ◽  
Yong Wang ◽  
Ziqi Xia ◽  
Lichun Wu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Thermal Gradient ◽  
Linear Response ◽  
Theoretical Study ◽  
Soret Coefficient ◽  
Thermal Gradients ◽  
Gradient Effect ◽  
Non Equilibrium Molecular Dynamics ◽  
Non Equilibrium

AbstractThe effect of the temperature gradient on the Soret coefficient in n-pentane/n-decane (n-C5/n-C10) mixtures was investigated using non-equilibrium molecular dynamics (NEMD) with the heat exchange (eHEX) algorithm. n-Pentane/n-decane mixtures with three different compositions (0.25, 0.5, and 0.75 mole fractions, respectively) and the TraPPE-UA force field were used in computing the Soret coefficient ({S_{T}}) at 300 K and 1 atm. Added/removed heat quantities (ΔQ) of 0.002, 0.004, 0.006, 0.008, and 0.01 kcal/mol were employed in eHEX processes in order to study the effect of different thermal gradients on the Soret coefficient. Moreover, a phenomenological description was applied to discuss the mechanism of this effect. Present results show that the Soret coefficient values firstly fluctuate violently and then become increasingly stable with increasing ΔQ (especially in the mixture with a mole fraction of 0.75), which means that ΔQ has a smaller effect on the Soret coefficient when the temperature gradient is higher than a certain thermal gradient. Thus, a high temperature gradient is recommended for calculating the Soret coefficient under the conditions that a linear response and constant phase are ensured in the system. In addition, the simulated Soret coefficient obtained at the highest ΔQ within three different compositions is in great agreement with experimental data.

Sign in / Sign up

Export Citation Format

Share Document