The Effect of Temperature on Defect Production by Displacement Cascades in alpha;-IRON

1996 ◽  
Vol 439 ◽  
Author(s):  
F. Gao ◽  
D. J. Bacon ◽  
P. E. J. Flewitt ◽  
T. A. Lewis
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Irradiation Temperature ◽  
Effect Of Temperature ◽  
Cascade Process ◽  
Thermal Spike ◽  
Defect Production ◽  
Alpha Iron ◽  
Displacement Cascades ◽  
The Continuum

AbstractMolecular dynamics (MD) simulations have been used to study the number and arrangement of defects produced by displacement cascades as functions of irradiation temperature, Tirr, in α-iron. The continuum treatment of heat conduction was used to adjust the temperature of the MD boundary atoms throughout the cascade process. This new hybrid model has been applied to cascades of either 2 or 5 keV at 100K, 400K, 600K and 900K. The number of Frenkel pairs decreases by about 20–30% as Tir increases from 100K to 900K, due to the increase in the lifetime of the thermal-spike phase. The same effect also brings about an increase in the proportion of selfinterstitial atoms that form clusters.

Molecular dynamics simulation of displacement cascades in Cu and Ni: Thermal spike behavior

1989 ◽  
Vol 4 (3) ◽  
pp. 579-586 ◽  
Author(s):  
T. Diaz de la Rubia ◽  
R. S. Averback ◽  
Horngming Hsieh ◽  
R. Benedek
Keyword(s):  
Molecular Dynamics ◽  
Marked Effect ◽  
Dynamics Simulation ◽  
Primary State ◽  
Thermal Spike ◽  
Defect Production ◽  
Displacement Cascades ◽  
Dynamics Simulations ◽  
Atomic Mixing ◽  
Kinetics Of

Molecular dynamics simulations of energetic displacement cascades in Cu and Ni were performed with primary-knock-on-atom (PKA) energies up to 5 keV. The interatomic forces were represented by the Gibson II (Cu) and the Johnson-Erginsoy (Ni) potentials. Our results indicate that the primary state of damage produced by displacement cascades is controlled basically by two phenomena: replacement collision sequences during the ballistic phase, and melting and resolidification during the thermal spike. The thermal-spike phase is of longer duration and has a more marked effect in Cu than in Ni. Results for atomic mixing, defect production, and defect clustering are presented and compared with experiment. Simulations of “heat spikes” in these metals suggest a model for “cascade collapse” based on the regrowth kinetics of the molten cascade core.

Computer Simulation of Defect Production and Behaviour in Displacement Cascades in Metals

1998 ◽  
Vol 540 ◽  
Author(s):  
D.J. Bacon ◽  
F. Gao ◽  
A.V. Barashev ◽  
Yu.N. Osetsky
Keyword(s):  
Computer Simulation ◽  
Radiation Damage ◽  
Defect Formation ◽  
Irradiation Temperature ◽  
Cascade Process ◽  
Successful Development ◽  
Defect Production ◽  
Displacement Cascades ◽  
Frenkel Defects ◽  
Atom Energy

AbstractRecent research using molecular dynamics to simulate radiation damage due to displacement cascades in metals is reviewed. It includes results dealing with the effect on defect formation of primary knock-on atom energy and irradiation temperature. Clear dependencies and trends have emerged in these areas. In terms of the development of models to describe the evolution of radiation damage microstructure, the important parameters are not only the total number of Frenkel defects but also the distribution of their population in clusters and the form and mobility of these clusters. Results on these aspects are reviewed and it is shown that computer simulation is providing detailed information that paves the way for successful development of models of the evolution of damage beyond the stage of the cascade process.

Computer Simulation of Defect Production and Behaviour in Displacement Cascades in Metals

1998 ◽  
Vol 538 ◽  
Author(s):  
D.J. Bacon ◽  
F. Gao ◽  
A.V. Barashev ◽  
Yu.N. Osetsky
Keyword(s):  
Computer Simulation ◽  
Radiation Damage ◽  
Defect Formation ◽  
Irradiation Temperature ◽  
Cascade Process ◽  
Successful Development ◽  
Defect Production ◽  
Displacement Cascades ◽  
Frenkel Defects ◽  
Atom Energy

AbstractRecent research using molecular dynamics to simulate radiation damage due to displacement cascades in metals is reviewed. It includes results dealing with the effect on defect formation of primary knock-on atom energy and irradiation temperature. Clear dependencies and trends have emerged in these areas. In terms of the development of models to describe the evolution of radiation damage microstructure, the important parameters are not only the total number of Frenkel defects but also the distribution of their population in clusters and the form and mobility of these clusters. Results on these aspects are reviewed and it is shown that computer simulation is providing detailed information that paves the way for successful development of models of the evolution of damage beyond the stage of the cascade process.

Computer Simulation of Displacement Cascades in α-Zirconium

1996 ◽  
Vol 439 ◽  
Author(s):  
F. Gao ◽  
S. J. Wooding ◽  
D. J. Bacon ◽  
A. F. Calder ◽  
L. M. Howe
Keyword(s):  
Computer Simulation ◽  
Production Efficiency ◽  
Md Simulations ◽  
Vacancy Cluster ◽  
Prism Plane ◽  
Defect Production ◽  
Displacement Cascades ◽  
Bcc Metals

AbstractThe damage produced in α-zirconium at 100 K by displacement cascades with energy up to 20 keV has been investigated by MD simulations. In agreement with modelling of fcc and bcc metals, the defect production efficiency in zirconium is well below the NRT estimate. The number and size of clusters, both vacancy and interstitial, are increased by increasing PKA energy, and clusters containing up to 25 interstitials and 30 vacancies were formed by 20 keV cascades. Most interstitial clusters have dislocation character with perfect Burgers vectors of the form 1/3<1120>, but a few metastable clusters are formed and are persistent over the timescale of MD simulations. Collapse of the 30-vacancy cluster to a faulted loop on the prism plane was found to occur over a period of more than 100 ps

scholarly journals Characterization of polystyrene under shear deformation using Molecular Dynamics

2021 ◽  
Author(s):  
Maximilian Ries ◽  
Paul Steinmann ◽  
Sebastian Pfaller
Keyword(s):  
Molecular Dynamics ◽  
Shear Deformation ◽  
Pure Shear ◽  
Material Model ◽  
Md Simulations ◽  
Constitutive Law ◽  
Coupling Scheme ◽  
Suitable Material ◽  
Continuum Description ◽  
The Continuum

Nano-filled polymers are becoming more and more important to meet the continuously growing requirements of modern engineering problems. The investigation of these composite materials at the molecular level, however, is either prohibitively expensive or just impossible. Multiscale approaches offer an elegant way to analyze such nanocomposites by significantly reducing computational costs compared to fully molecular simulations.When coupling different time and length scales, however, it is in particular important to ensure that the same material description is applied at each level of resolution.The Capriccio method, for instance, couples a particle domain modeled with molecular dynamics (MD) with a finite element based continuum description and has been used i.a. to investigate the effects of nano-sized silica additives embedded in atactic polystyrene (PS). However, a simple hyperelastic constitutive law is used so far for the continuum description which is not capable to fully match the behavior of the particle domain. To overcome this issue and to enable further optimization of the coupling scheme, the material model used for the continuum should be derived directly from pure MD simulations under thermodynamic conditions identical to those used by the Capriccio method.To this end, we analyze the material response of pure PS under uniaxial deformation using strain-controlled MD simulations. Analogously, we perform simulations under pure shear deformation to obtain a comprehensive understanding of the material behavior.As a result, the present PS shows viscoelastic characteristics for small strains, whereas viscoplasticity is observed for larger deformations. The insights gained and data generated are used to select a suitable material model whose parameters have to be identified in a subsequent parameter optimization.

Molecular Dynamics Simulations to Evaluate the Effect of the Difference in Material Properties on Irradiation-Induced Defect Formation Under Applied Strain

2012 ◽  
Author(s):  
Toshihiro Horinouchi ◽  
Satoshi Miyashiro ◽  
Mitsuhiro Itakura ◽  
Taira Okita
Keyword(s):  
Molecular Dynamics ◽  
Defect Formation ◽  
Stacking Fault ◽  
Applied Strain ◽  
Stacking Fault Energy ◽  
Cascade Process ◽  
Defect Production ◽  
Fcc Metals ◽  
The Difference ◽  
Dynamics Simulations

The influence of applied strain on the defect production rate during a cascade process was evaluated for several FCC metals with different Stacking Fault Energy by the method of molecular dynamics. It was found that applied strain increases the number of surviving defects, which is caused by the enhanced formation of larger clusters. It was also found that the number of defects is almost independent of Stacking Fault Energy even under applied strain.

Validity of Molecular Dynamics by Quantum Mechanics

2013 ◽  
Author(s):  
Thomas Prevenslik
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Quantum Mechanics ◽  
Statistical Mechanics ◽  
Quantum Electrodynamics ◽  
Md Simulations ◽  
Tensile Tests ◽  
Electron Pairs ◽  
Linear Motors ◽  
The Continuum

MD is commonly used in computational physics to determine the atomic response of nanostructures. MD stands for molecular dynamics. With theoretical basis in statistical mechanics, MD relates the thermal energy of the atom to its momentum by the equipartition theorem. Momenta of atoms in an ensemble are determined by solving Newton’s equations with inter-atomic forces derived from Lennard-Jones potentials. MD therefore assumes the atom always has heat capacity as otherwise the momenta of the atoms cannot be related to their temperature. In bulk materials, the continuum is simulated in MD by imposing PBC on an ensemble of atoms, the atoms always having heat capacity. PBC stands for periodic boundary conditions. MD simulations of the bulk are valid because atoms in the bulk do indeed have heat capacity. Nanostructures differ from the bulk. Unlike the continuum, the atom confined in discrete submicron geometries is precluded by QM from having the heat capacity necessary to conserve absorbed EM energy by an increase in temperature. QM stands for quantum mechanics and EM for electromagnetic. Quantum corrections of MD solutions that would show the heat capacity of nanostructures vanishes are not performed. What this means is the MD simulations of discrete nanostructures in the literature not only have no physical meaning, but are knowingly invalid by QM. In the alternative, conservation of absorbed EM energy is proposed to proceed by the creation of QED induced non-thermal EM radiation at the TIR frequency of the nanostructure. QED stands for quantum electrodynamics and TIR for total internal reflection. The QED radiation creates excitons (holon and electron pairs) that upon recombination produce EM radiation that charges the nanostructure or is emitted to the surroundings — a consequence only possible by QM as charge is not created in statistical mechanics. Invalid discrete MD simulations are illustrated with nanofluids, nanocars, linear motors, and sputtering. Finally, a valid MD simulation by QM is presented for the stiffening of NWs in tensile tests. NW stands for nanowire.

scholarly journals Molecular Dynamics Reveals the Effects of Temperature on Critical SARS-CoV-2 Proteins

2021 ◽  
Author(s):  
Paul Morgan ◽  
Chih-Wen Shu
Keyword(s):  
Molecular Dynamics ◽  
Drug Targets ◽  
Rna Virus ◽  
Nonstructural Protein ◽  
Md Simulations ◽  
Effect Of Temperature ◽  
Temperature Variations ◽  
Serious Infection ◽  
Critical Residues ◽  
The Stability

ABSTRACTSevere Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a newly identified RNA virus that causes the serious infection Coronavirus Disease 2019 (COVID-19). The incidence of COVID-19 is still increasing worldwide despite the summer heat and cool winter. However, little is known about seasonal stability of SARS-CoV-2. Herein, we employ Molecular Dynamics (MD) simulations to explore the effect of temperature on four critical SARS-CoV-2 proteins. Our work demonstrates that the spike Receptor Binding Domain (RBD), Main protease (Mpro), and nonstructural protein 3 (macro X) possesses extreme thermos-stability when subjected to temperature variations rendering them attractive drug targets. Furthermore, our findings suggest that these four proteins are well adapted to habitable temperatures on earth and are largely insensitive to cold and warm climates. Furthermore, we report that the critical residues in SARS-CoV-2 RBD were less responsive to temperature variations as compared to the critical residues in SARS-CoV. As such, extreme summer and winter climates, and the transition between the two seasons, are expected to have a negligible effect on the stability of SARS-CoV-2 which will marginally suppress transmission rates until effective therapeutics are available world-wide.

Atomistic Simulation of Displacement Cascades in Zircon

2002 ◽  
Vol 713 ◽  
Author(s):  
R. Devanathan ◽  
William J. Weber ◽  
L. Rene Corrales
Keyword(s):  
Molecular Dynamics ◽  
Atomistic Simulation ◽  
Short Range ◽  
Md Simulations ◽  
Low Energy ◽  
Vacancy Clusters ◽  
Displacement Cascades ◽  
Buckingham Potential ◽  
Long Range Interactions ◽  
Ring Mechanism

ABSTRACTLow-energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics (MD) simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements are found to occur mainly in the O sublattice, and O replacements by a ring mechanism are predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects are found to occur. This Si-O-Si bridging is considerable in ZrSiO4 quenched from the melt in MD simulations.

Sign in / Sign up

Export Citation Format

Share Document