Dislocation Mobilities in NiAl From Molecular Dynamics Simulations

1990 ◽  
Vol 209 ◽  
Author(s):  
A. Moncevicz ◽  
P. C. Clapp ◽  
J. A. Rifkin
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Dislocation Core ◽  
Alloy System ◽  
Shear Velocity ◽  
Peierls Stress ◽  
Al Alloy ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Edge Dislocations

ABSTRACTUsing the Voter-Chen Embedded Atom Method (EAM) potentials for the Ni-Al alloy system,the Peierls stress (σp) and velocity of edge dislocations (b=[100]) have been estimated in stoichiometric perfectly ordered B2 NiAIat a temperature of 10 K, by the use of molecular dynamics simulations employing approximately 4000 atoms. σp was determined to be about 3×1010 dynes/cm2, or about 2%of the shear modulus, C44. The steady state velocity was found to be about 1.6×105 cm/s (or 65% of the (001) shear velocity) under an applied shear stress of 3.9×1010 dynes/cm2. Stress induced martensite (SIM) was nucleated in some of the simulations after the dislocation had begun to move, and in all cases when the SIM reached the immediate neighborhood of the dislocation core the motion of the dislocation was arrested.

An Atomistic Study of Hydrogen Effects on the Fracture of Tilt Boundaries in Nickel.

1991 ◽  
Vol 238 ◽  
Author(s):  
N. R. Moody ◽  
S. M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Site Occupancy ◽  
Boundary Structure ◽  
Trap Site ◽  
Embedded Atom ◽  
Defect Sites ◽  
Tilt Boundaries ◽  
Temperature Exposure ◽  
Dynamics Simulations

ABSTRACTIn this study, molecular dynamics simulations were used to fracture Σ9 tilt boundaries in nickel lattices containing a range of trap site hydrogen concentrations. These lattices were created in a previous study using Monte Carlo simulations and the Embedded Atom Method to duplicate room temperature exposure to a hydrogen environment. The molecular dynamics simulations were run at absolute zero to immobilize the hydrogen distributions for determination of trap site occupancy effects on grain boundary fracture. In all lattices, fracture began by the breaking of bonds next to polyhedral defect sites that characterize the boundary structure followed by rapid failure of the remaining bonds. The effect of hydrogen was to lower the stress for fracture from 18 GPa to a lower limiting value of 8 GPa as the trap sites along the boundary plane filled. The simulations showed that the atoms at these sites were the only atoms involved in the fracture process. Within the constraints imposed on these calculations, the results of this study showed that the ‘inherent’ effect of hydrogen in the absence of plastic deformation is to reduce the cohesive force between atoms across the boundary.

Study on the structural transition of CoNi nanoclusters using molecular dynamics simulations

2018 ◽  
Vol 32 (11) ◽  
pp. 1850133
Author(s):  
J. H. Xia ◽  
Xue-Mei Gao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Structural Transition ◽  
Correction Function ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Analysis Technique ◽  
Dynamics Simulations ◽  
Embedded Atom Method Potential ◽  
Pair Analysis

In this work, the segregation and structural transitions of CoNi clusters, between 1500 and 300 K, have been investigated using molecular dynamics simulations with the embedded atom method potential. The radial distribution function was used to analyze the segregation during the cooling processes. It is found that Co atoms segregate to the inside and Ni atoms preferably to the surface during the cooling processes, the Co[Formula: see text]Ni[Formula: see text] cluster becomes a core–shell structure. We discuss the structural transition according to the pair-correction function and pair-analysis technique, and finally the liquid Co[Formula: see text]Ni[Formula: see text] crystallizes into the coexistence of hcp and fcc structure at 300 K. At the same time, it is found that the frozen structure of CoNi cluster is strongly related to the Co concentration.

MOLECULAR DYNAMICS SIMULATIONS OF STRUCTURAL PROPERTIES OF CuNi ALLOYS DURING THE COOLING PROCESS AT HIGH PRESSURE

2020 ◽  
Vol 65 (10) ◽  
pp. 10-17
Author(s):  
Thao Nguyen Thi ◽  
Giang Bui Thi Ha ◽  
Linh Tran Phan Thuy ◽  
Hop Nguyen Van ◽  
Chung Pham Do ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
High Pressure ◽  
Molecular Dynamics Simulations ◽  
Sudden Change ◽  
Face Centered Cubic ◽  
Cooling Process ◽  
Embedded Atom ◽  
The Face ◽  
Face Centered ◽  
Dynamics Simulations

Molecular dynamics simulations of Cu80Ni20 (Cu:Ni = 8:2) model with the size of 8788 atoms have been carried out to study the structure and mechanical behavior at high pressure of 45 GPa. The interactions between atoms of the system were calculated by the Quantum Sutton-Chen embedded-atom potentials. The crystallization has occurred during the cooling process with a cooling rate of 0.01 K\ps. The temperature range of the phase transition is determined based on the sudden change of atomic potential during the cooling process. There is also a sudden change in the number of individual atoms in the sample. At a temperature of 300 K, both Ni and Cu atoms are crystallized into the face-centered cubic (FCC) and the hexagonal close-packed (HCP) phases, respectively. The mechanical characteristics of the sample at 300 K were also analyzed in detail through the determination of elastic modulus, number of atoms, and void distribution during the tensile process.

Direct Molecular Dynamics Simulations of Diffusion Mechanisms in NiAl

2000 ◽  
Vol 646 ◽  
Author(s):  
D. Farkas ◽  
B. Soulé de Bas
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Molecular Dynamics Simulations ◽  
Sequential Analysis ◽  
Nearest Neighbor ◽  
Interatomic Potential ◽  
Embedded Atom ◽  
Diffusion Mechanisms ◽  
Dynamics Simulations ◽  
Potential Diffusion

ABSTRACTMolecular dynamics simulations of the diffusion process in ordered B2 NiAl at high temperature were performed using an embedded atom interatomic potential. Diffusion occurs through a variety of cyclic mechanisms that accomplish the motion of the vacancy through nearest neighbor jumps restoring order to the alloy at the end of the cycle. The traditionally postulated 6-jump cycle is only one of the various cycles observed and some of these are quite complex. A detailed sequential analysis of the observed 6-jump cycles was performed and the results are analyzed in terms of the activation energies for individual jumps calculated using molecular statics simulations.

scholarly journals Impact of screw and edge dislocations on the thermal conductivity of individual nanowires and bulk GaN: a molecular dynamics study

2018 ◽  
Vol 20 (7) ◽  
pp. 5159-5172 ◽  
Author(s):  
Konstantinos Termentzidis ◽  
Mykola Isaiev ◽  
Anastasiia Salnikova ◽  
Imad Belabbas ◽  
David Lacroix ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Transport Properties ◽  
Thermal Transport ◽  
Thermal Transport Properties ◽  
Bulk Gan ◽  
Dynamics Simulations ◽  
Edge Dislocations

The thermal transport properties of nanowires and bulk GaN in the presence of different dislocations using molecular dynamics simulations are reported.

Some Thermodynamic Properties of NiAl Calculated by Molecular Dynamics Simulations

1988 ◽  
Vol 133 ◽  
Author(s):  
P. C. Clapp ◽  
M. J. Rubins ◽  
S. Charpenay ◽  
J. A. Rifkin ◽  
Z. Z. Yu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Boundary Energy ◽  
Alloy System ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Surface Energies ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Anti Phase Boundary

ABSTRACTCalculations of the surface free energy and anti-phase boundary energy as a function of low index orientations and temperature have been determined for equiatomic perfectly ordered bcc NiAl via molecular dynamics computer simulations. The simulations utilized an Embedded Atom Method calculation of the interatomic potentials and volume forces in the Ni-As alloy system. Values of about 0.95, 1.6, 1.9 and 2.0 J/m2 were found for surface energies of the {100}, {110}, {112} and {111} orientations:, respectively. APB energies of about 0.24 and 0.38 J/m2 were determined for {110} and {112} boundaries, respectively. In addition, we have examined the phase stability and relative energies of the ordered bcc, fcc and bct phases at low temperature, and find a bct phase with c/a = 1.32 slightly lower in energy than the bcc, presaging the martensitic transformation that occurs at finite temperatures in more nickel rich alloys.

Cascade Overlap in hcp Zirconium: Defect Accumulation and Microstructure Evolution with Radiation using Molecular Dynamics Simulations

2013 ◽  
Vol 1514 ◽  
pp. 37-42 ◽  
Author(s):  
Prithwish K. Nandi ◽  
Jacob Eapen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Microstructure Evolution ◽  
Stacking Faults ◽  
Embedded Atom Method ◽  
Shockley Partial Dislocation ◽  
Embedded Atom ◽  
Defect Accumulation ◽  
Dynamics Simulations ◽  
Eam Potential

ABSTRACTMolecular dynamics simulations are performed to investigate the defect accumulation and microstructure evolution in hcp zirconium (Zr) – a material which is widely used as clad for nuclear fuel. Cascades are generated with a 3 keV primary knock-on atom (PKA) using an embedded atom method (EAM) potential with interactions modified for distances shorter than 0.1 Å. With sequential cascade simulations we show the emergence of stacking faults both in the basal and prism planes, and a Shockley partial dislocation on the basal plane.

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