On The Mechanism of Interstitial Cluster Migration in α -FE

1998 ◽  
Vol 540 ◽  
Author(s):  
A.V. Barashev ◽  
Yu.N. Osetsky ◽  
D.J. Bacon
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulations ◽  
Microstructure Evolution ◽  
Pure Copper ◽  
Simple Relationship ◽  
Statistical Accuracy ◽  
Jump Frequency ◽  
Temperature Range ◽  
Thermally Activated ◽  
Centre Of Gravity

AbstractRecent molecular dynamics (MD) computer simulations have shown that clusters consisting of up to a few tens of self-interstitial atoms (SIAs) are highly mobile along closed-packed crystallographic directions in pure copper and iron. This effect has important consequences for microstructure evolution in irradiated metals and so it is desirable to investigate the mechanisms of the cluster motion. In the present paper the results of MD modelling of the thermally-activated motion of clusters of 3, 9 and 17 SIAs in α-Fe in the temperature range from 90 to 1400 K are analyzed. The extensive MD data has enabled the migration of clusters, as well as that of individual SIAs in the clusters, to be treated with high statistical accuracy. The correlation between the motion of the centre of gravity of a cluster and the jumps of individual SIAs in the cluster is revealed. It is found that the SIAs in a cluster jump almost independently and their jump frequency depends on the number of SIAs in the cluster. This leads to a simple relationship between the jump frequency of a cluster and the number of SIAs in it. The cluster jump frequency exhibits a deviation from the Arrhenius relationship. The reason for this is discussed.

scholarly journals Simulation of Mechanical Deformation and Tribology of Nano-Thin Amorphous Hydrogenated Carbon (a:Ch) Films Using Molecular Dynamics

1996 ◽  
Vol 436 ◽  
Author(s):  
J. N. Glosli ◽  
M. R. Philpott ◽  
J. Belak
Keyword(s):  
Molecular Dynamics ◽  
Substrate Temperature ◽  
Computer Simulations ◽  
Mechanical Deformation ◽  
Porous Graphite ◽  
Pure Carbon ◽  
Substrate Temperatures ◽  
Amorphous Hydrogenated Carbon ◽  
Deposition Energy

AbstractMolecular dynamics computer simulations are used to study the effect of substrate temperature on the microstructure of deposited amorphous hydrogenated carbon (a:CH) films. A transition from dense diamond-like films to porous graphite-like films is observed between substrate temperatures of 400K and 600K for a deposition energy of 20 eV. The dense a:CH film grown at 300K and 20 eV has a hardness (˜50 GPa) about half that of a pure carbon (a:C) film grown under the same conditions.

Structural and dynamical properties of 13-atom Cu–Co mixed clusters

2021 ◽  
Author(s):  
Shi-Wei Ren
Keyword(s):  
Molecular Dynamics ◽  
Pure Copper ◽  
Similarity Function ◽  
Step Process ◽  
Pure Cobalt ◽  
Pair Separation ◽  
Dynamical Properties ◽  
Mixed Clusters ◽  
Dynamics Method ◽  
Relative Root

In this paper, the geometric structures and the melting-like processes of the 13-atom pure copper, pure cobalt cluster and their 13-atom mixed clusters are investigated and compared by the molecular dynamics method. The calculation shows that the pure copper and cobalt clusters have the standard icosahedral structures and the mixed clusters take on the deformed icosahedral structures. The quantitative analysis shows that the deformations are slight. Moreover, an element similarity function is introduced by which the contribution of the compositions of the clusters to the deformation of the mixed clusters is analyzed and discussed. With the increase of the temperature, the migrating and recombination of the atoms on the surface of the clusters are observed, indicating the starting of the transition from solid-like to liquid-like state for the clusters. Through the calculating of the relative root-mean-squared pair separation fluctuation and monitoring the dynamical structures of the clusters, it is found that the mixed clusters experience a multi-step process in the transition.

Microstructure evolution and plastic deformation of Ni47Co53 alloy under tension

CrystEngComm ◽  
2022 ◽  
Author(s):  
ruibo ma ◽  
Lili Zhou ◽  
Yong-Chao Liang ◽  
Ze-an Tian ◽  
Yun-Fei Mo ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Rapid Solidification ◽  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Cooling Rates ◽  
Solidification Processes ◽  
Molecular Dynamics Methods

To investigate microstructural evolution and plastic deformation under tension conditions, the rapid solidification processes of Ni47Co53 alloy are first simulated by molecular dynamics methods at cooling rates of 1011, 1012...

Computer Simulation Studies of Fracture in Vitreous Silica

2002 ◽  
Vol 731 ◽  
Author(s):  
Romulo Ochoa ◽  
Michael Arief ◽  
Joseph H. Simmons
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Computer Simulations ◽  
Silica Glass ◽  
Vitreous Silica ◽  
Uniaxial Strain ◽  
Force Function ◽  
Simulation Studies ◽  
Previous Fracture ◽  
Computer Simulation Studies

AbstractWe conduct molecular dynamics computer simulations of fracture in silica glass using the van Beest, Kramer, and van Santen model. Stress is applied by uniaxial strain at different pulling rates. Comparisons with previous fracture simulations of silica that used the Soules force function are presented. We find that in both models stress is relieved by rotation of the (SiO4)-2 tetrahedrons, increasing Si-O-Si bonding angles, and only small changes in the tetrahedron dimensions and O-Si-O angles.

An anomaly in the specific heat below 3 °K of copper containing hydrogen

1969 ◽  
Vol 47 (14) ◽  
pp. 1485-1491 ◽  
Author(s):  
Neil Waterhouse
Keyword(s):  
Specific Heat ◽  
Molecular Hydrogen ◽  
Pure Copper ◽  
Solid Hydrogen ◽  
Rotational State ◽  
Experimental Results ◽  
Ortho Hydrogen ◽  
Temperature Range ◽  
A Value ◽  
Heat Curve

The specific heat of copper heated in hydrogen at 1040 °C has been measured over the temperature range 0.4 to 3.0 °K and found to be anomalous. The anomaly occurs in the same temperature range as the solid hydrogen λ anomaly which, in conjunction with evidence of ortho to para conversion of hydrogen in the sample, suggests the presence of molecular hydrogen in the copper. The anomaly reported by Martin for "as-received" American Smelting and Refining Company (ASARCO) 99.999+ % pure copper has been briefly compared with the present results. The form of the anomaly produced by the copper-hydrogen specimen has been compared with Schottky curves using the simplest possible model, that for two level splitting of the degenerate J = 1 rotational state of the ortho-hydrogen molecule.Maintenance of the copper-hydrogen sample at ~20 °K for approximately 1 week removed the "hump" in the specific heat curve. An equation of the form Cp = γT + (464.34/(θ0c)3)T3 was found to fit these experimental results and produced a value for γ which had increased over that for vacuumannealed pure copper by ~2%.

scholarly journals Short Pyridine-Furan Springs Exhibit Bistable Dynamics of Duffing Oscillators

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3264
Author(s):  
Vladik A. Avetisov ◽  
Maria A. Frolkina ◽  
Anastasia A. Markina ◽  
Alexander D. Muratov ◽  
Vladislav S. Petrovskii
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Stochastic Resonance ◽  
Duffing Oscillator ◽  
Molecular Structures ◽  
Thermally Activated ◽  
Responsive Polymers ◽  
Bistable Dynamics ◽  
Dynamics Simulations ◽  
Intensive Development

The intensive development of nanodevices acting as two-state systems has motivated the search for nanoscale molecular structures whose dynamics are similar to those of bistable mechanical systems, such as Euler arches and Duffing oscillators. Of particular interest are the molecular structures capable of spontaneous vibrations and stochastic resonance. Recently, oligomeric molecules that were a few nanometers in size and exhibited the bistable dynamics of an Euler arch were identified through molecular dynamics simulations of short fragments of thermo-responsive polymers subject to force loading. In this article, we present molecular dynamics simulations of short pyridine-furan springs a few nanometers in size and demonstrated the bistable dynamics of a Duffing oscillator with thermally-activated spontaneous vibrations and stochastic resonance.

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