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Leonid V Zhigilei - One of the best experts on this subject based on the ideXlab platform.
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erratum computational study of the generation of crystal defects in a Bcc Metal target irradiated by short laser pulses phys rev b 77 214108 2008
Physical Review B, 2011Co-Authors: Lin Zhibin, R.a. Johnson, Leonid V ZhigileiAbstract:In two places on page 7 and in the caption of Fig. 7, the plane of the stacking fault (slip plane) is mistakenly identified as (100) instead of (101). The text should be as follows: “. . .the stacking fault is created by dividing the system into two parts by a (101) plane. . .” at the bottom of the left column on page 7; “. . .the atoms are allowed to relax in the direction perpendicular to the (101) slip plane. . .” at the top of the right column of page 7; “Generalized stacking fault energy, γGSF, for the (101) slip plane in Bcc EAM Cr. . .” in the caption for Figure 7 on page 8. These are typing errors and they do not affect the results reported in the paper.
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computational study of the generation of crystal defects in a Bcc Metal target irradiated by short laser pulses
Physical Review B, 2008Co-Authors: R.a. Johnson, Leonid V ZhigileiAbstract:The generation of crystal defects in a Cr target irradiated by a short, 200 fs, laser pulse is investigated in computer simulations performed with a computational model that combines the classical molecular dynamics method with a continuum description of the laser excitation of conduction band electrons, electron-phonon coupling, and electron heat conduction. Interatomic interactions are described by the embedded atom method EAM potential with a parametrization designed for Cr. The potential is tested by comparing the properties of the EAM Cr material with experimental data and predictions of density functional theory calculations. The simulations are performed at laser fluences close to the threshold for surface melting. Fast temperature variation and strong thermoelastic stresses produced by the laser pulse are causing surface melting and epitaxial resolidification, transient appearance of a high density of stacking faults along the 110 planes, and generation of a large number of point defects vacancies and self-interstitials. The stacking faults appear as a result of internal shifts in the crystal undergoing a rapid uniaxial expansion in the direction normal to the irradiated surface. The stacking faults are unstable and disappear shortly after the laser-induced tensile stress wave leaves the surface region of the target. Thermally activated generation of vacancy-interstitial pairs during the initial temperature spike and quick escape of highly mobile self-interstitials to the melting front or the free surface of the target, along with the formation of vacancies at the solid-liquid interface during the fast resolidification process, result in a high density of vacancies, on the order of 10 3 per lattice site, created in the surface region of the target. The strong supersaturation of vacancies can be related to the incubation effect in multipulse laser ablation/damage and should play an important role in mixing/alloying of multicomponent or composite targets.
R B Gerber - One of the best experts on this subject based on the ideXlab platform.
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simulations of hydrogen diffusion on Bcc Metal 110 surfaces coverage and temperature dependence
Surface Science, 2000Co-Authors: E S Altshuler, D L Mills, R B GerberAbstract:Abstract We study the coverage and temperature dependences of the tracer diffusion coefficient for a chemisorbed layer of interacting hydrogen atoms on a model of a Bcc Metal (110) surface. The surface is rigid, and the short bridge barriers between adjacent chemisorption wells are sufficiently low that hydrogen atoms diffuse actively across the surface, on a time scale compatible with our molecular dynamics simulations. We deduce the coverage dependence of the effective activation barrier and the prefactor. We also examine, as a function of coverage, the percentage of jumps from singly occupied to either empty or occupied chemisorption wells, and from doubly occupied wells to empty or singly occupied wells. Although the effective activation barrier deduced from the numerical data exhibits a weak dependence on coverage, as found in data on H diffusion on the W(110) surface, the percentage of jumps of the types mentioned varies dramatically. The prefactor in the diffusion constant extracted from the simulations agrees well with elementary expectations for the rigid surface, but is much larger than that found experimentally. Finally, the low coverage tracer diffusivity is found to be appreciably anisotropic. The anisotropy decreases substantially as coverage increases.
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solid and liquid like phases of chemisorbed hydrogen monolayers on Bcc Metal surfaces structure dynamics and order disorder transition
Surface Science, 1998Co-Authors: E S Altshuler, D L Mills, R B GerberAbstract:Abstract The structural and dynamical properties of a saturated chemisorbed hydrogen monolayer on a model Bcc(110) Metal surface were studied by molecular dynamics simulations over a range of temperatures from 100 to 300 K. The potential function used, including both the hydrogen/Metal interaction and the interactions between the hydrogens, was calibrated in part from experimental data. At low temperatures, the monolayer has an ordered, broken symmetry state with regard to the underlying Metal surface. As temperature is increased, an order–disorder transition takes place. We report studies of static and dynamical structure factors, of pertinent order parameters and, where applicable, of phonon dispersion in order to gain insight into the phases. The disordered phase exhibits anisotropy with uniaxial short-range order. We comment on the relation of the results to recent experimental studies of H/W(110) and H/Mo(110), and suggest future experiments to explore the high temperature phase.
R.a. Johnson - One of the best experts on this subject based on the ideXlab platform.
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erratum computational study of the generation of crystal defects in a Bcc Metal target irradiated by short laser pulses phys rev b 77 214108 2008
Physical Review B, 2011Co-Authors: Lin Zhibin, R.a. Johnson, Leonid V ZhigileiAbstract:In two places on page 7 and in the caption of Fig. 7, the plane of the stacking fault (slip plane) is mistakenly identified as (100) instead of (101). The text should be as follows: “. . .the stacking fault is created by dividing the system into two parts by a (101) plane. . .” at the bottom of the left column on page 7; “. . .the atoms are allowed to relax in the direction perpendicular to the (101) slip plane. . .” at the top of the right column of page 7; “Generalized stacking fault energy, γGSF, for the (101) slip plane in Bcc EAM Cr. . .” in the caption for Figure 7 on page 8. These are typing errors and they do not affect the results reported in the paper.
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computational study of the generation of crystal defects in a Bcc Metal target irradiated by short laser pulses
Physical Review B, 2008Co-Authors: R.a. Johnson, Leonid V ZhigileiAbstract:The generation of crystal defects in a Cr target irradiated by a short, 200 fs, laser pulse is investigated in computer simulations performed with a computational model that combines the classical molecular dynamics method with a continuum description of the laser excitation of conduction band electrons, electron-phonon coupling, and electron heat conduction. Interatomic interactions are described by the embedded atom method EAM potential with a parametrization designed for Cr. The potential is tested by comparing the properties of the EAM Cr material with experimental data and predictions of density functional theory calculations. The simulations are performed at laser fluences close to the threshold for surface melting. Fast temperature variation and strong thermoelastic stresses produced by the laser pulse are causing surface melting and epitaxial resolidification, transient appearance of a high density of stacking faults along the 110 planes, and generation of a large number of point defects vacancies and self-interstitials. The stacking faults appear as a result of internal shifts in the crystal undergoing a rapid uniaxial expansion in the direction normal to the irradiated surface. The stacking faults are unstable and disappear shortly after the laser-induced tensile stress wave leaves the surface region of the target. Thermally activated generation of vacancy-interstitial pairs during the initial temperature spike and quick escape of highly mobile self-interstitials to the melting front or the free surface of the target, along with the formation of vacancies at the solid-liquid interface during the fast resolidification process, result in a high density of vacancies, on the order of 10 3 per lattice site, created in the surface region of the target. The strong supersaturation of vacancies can be related to the incubation effect in multipulse laser ablation/damage and should play an important role in mixing/alloying of multicomponent or composite targets.
Jean-hubert Schmitt - One of the best experts on this subject based on the ideXlab platform.
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Experimental characterization and mechanical behaviour modelling of molybdenum-titanium carbide composite for high temperature applications
International Journal of Refractory Metals and Hard Materials, 2009Co-Authors: Denis Cédat, Maximilien Libert, Marion Le Flem, Olivier Fandeur, Colette Rey, Michel Clavel, Jean-hubert SchmittAbstract:Simulations of the elastic-viscoplastic behaviour of ceramic-Metal composite, over the temperature range 298-993 K, \are performed on realistic aggregates built up from electron back scatter diffraction methods. Physical based constitutive models are developed in order to characterize the deformation behaviour of body centered cubic (Bcc) Metal and face centered cubic (fcc) ceramic under various temperatures. While the ceramic keeps elastic, the viscoplastic behaviour of the Metal part is described with a dislocation - based model, implemented in the finite element code ABAQUS, in order to compute local strain and stress fields during compressive tests. It is shown that the adopted constitutive laws are able to give back local complex experimental evidence on weak points of the microstructure. (C) 2008 Elsevier Ltd. All rights reserved.
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Experimental characterization and mechanical behaviour modelling of Molybdenum -Titanium Carbide composite for high temperature applications.
International Journal of Refractory Metals and Hard Materials, 2009Co-Authors: Cédat Denis, Maximilien Libert, Marion Le Flem, Olivier Fandeur, Colette Rey, Michel Clavel, Jean-hubert SchmittAbstract:Simulations of the elastic-viscoplastic behaviour of ceramic-Metal composite, over the temperature range 298-993K, are performed on realistic aggregates built up from Electron Back Scatter Diffraction methods. Physical based constitutive models are developed in order to characterize the deformation behaviour of body centered cubic (Bcc) Metal and face centered cubic (fcc) ceramic under various temperatures. While the ceramic keeps elastic, the viscoplastic behaviour of the Metal part is described with a dislocation - based model, implemented in the finite element code ABAQUS, in order to compute local strain and stress fields during compressive tests. It is shown that the adopted constitutive laws are able to give back local complex experimental evidence on weak points of the microstructure.
Vasily V. Bulatov - One of the best experts on this subject based on the ideXlab platform.
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dislocation motion in Bcc Metals by molecular dynamics
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: Jinpeng Chang, Vasily V. BulatovAbstract:Abstract We performed molecular dynamics (MD) simulation of edge dislocations in Bcc Metal Mo with 1/2〈1 1 1〉 Burgers vector gliding on (1 1 0) plane using the Finnis–Sinclair N-body empirical potential and periodic boundary conditions (PBC). The profile of dislocation line, extracted from atomic displacements during MD simulation, suggests a dominant mechanism of double-kink nucleation, without appreciable kink migration. This observation is consistent with further simulations in which dislocations with pre-existing kinks are observed to move at the same velocity as the initially straight dislocations. Our results show a linear stress dependence of the dislocation velocity and a decrease of mobility with increasing temperature, both features interpreted as signifying that the simulations pertain to the viscous phonon drag regime of dislocation mobility.
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Molecular dynamics study of edge dislocation motion in a Bcc Metal
Journal of Computer-Aided Materials Design, 1999Co-Authors: Jinpeng Chang, Vasily V. BulatovAbstract:The motion of an edge dislocation gliding in a Bcc lattice under shear loading is simulated by molecular dynamics. The time evolution of the dislocation profile, derived by analyzing the spatial disregistry between two adjacent atomic rows, reveals frequent nucleation of double kinks and little activity in kink migration in association with the dislocation motion. An essentially linear stress variation is obtained, while the temperature dependence suggests the mechanism of phonon drag.