Molecular dynamics simulations of He bubble nucleation at grain boundaries.
Summary of "Molecular dynamics simulations of He bubble nucleation at grain boundaries."
The nucleation behavior of He bubbles in single-crystal (sc) and nano-grain body-centered-cubic (bcc) Mo is simulated using molecular dynamics (MD) simulations, focusing on the effects of the grain boundary (GB) structure. In sc Mo, the nucleation behavior of He bubbles depends on irradiation conditions. He bubbles nucleate by either clustering of He atoms with pre-existing vacancies or self-interstitial-atom (SIA) punching without initial vacancies. In nano-grain Mo, strong precipitation of He at the GBs is observed, and the density, size and spatial distribution of He bubbles vary with the GB structure. The corresponding He bubble density is higher in nano-grain Mo than that in sc Mo and the average bubble size is smaller. In the GB plane, He bubbles distribute along the dislocation cores for GBs consisting of GB dislocations and randomly for those without distinguishable dislocation structures. The simulation results in nano-grain Mo are in agreement with previous experiments in metal nano-layers, and they are further explained by the effect of excess volume associated with the GBs.
Affiliation
Fuels Modeling and Simulation, Idaho National Laboratory (INL), Idaho Falls, ID 83415, USA.
Journal Details
This article was published in the following journal.
Name: Journal of physics. Condensed matter : an Institute of Physics journal
ISSN: 1361-648X
Pages: 305005
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22722319
- DOI: http://dx.doi.org/10.1088/0953-8984/24/30/305005
Medical and Biotech [MESH] Definitions
Molecular Dynamics Simulation
A computer simulation developed to study the motion of molecules over a period of time.
Secale Cereale
A hardy grain crop, rye, grown in northern climates. It is the most frequent host to ergot (CLAVICEPS), the toxic fungus. Its hybrid with TRITICUM is TRITICALE, another grain.
Gastric Balloon
An inflatable device implanted in the stomach as an adjunct to therapy of morbid obesity. Specific types include the silicone Garren-Edwards Gastric Bubble (GEGB), approved by the FDA in 1985, and the Ballobes Balloon.
Nonlinear Dynamics
The study of systems which respond disproportionately (nonlinearly) to initial conditions or perturbing stimuli. Nonlinear systems may exhibit "chaos" which is classically characterized as sensitive dependence on initial conditions. Chaotic systems, while distinguished from more ordered periodic systems, are not random. When their behavior over time is appropriately displayed (in "phase space"), constraints are evident which are described by "strange attractors". Phase space representations of chaotic systems, or strange attractors, usually reveal fractal (FRACTALS) self-similarity across time scales. Natural, including biological, systems often display nonlinear dynamics and chaos.
Kinetics
The rate dynamics in chemical or physical systems.
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