Atomistic Ordering in Body Centered Cubic Uranium-Zirconium Alloy

ABSTRACTThe metallic binary-alloy fuel Uranium-Zirconium is important for the use of the new generation of advanced fast reactors. Uranium-Zirconium goes through a phase transition at higher temperatures to a (gamma) Body Centered Cubic (BCC) phase. The BCC high temperature phase is particularly important, since the BCC phase corresponds to the temperature range in which the fast reactors will operate. A semi-empirical MEAM (Modified Embedded Atom Method) potential is presented for Uranium-Zirconium. The physical properties of the Uranium-Zirconium binary alloy were reproduced using Molecular Dynamics (MD) simulations and Monte Carlo (MC) simulations with the MEAM potential. This is a large step in making a computationally acceptable fuel performance code.

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Embedded-atom-method functions for the body-centered-cubic iron and hydrogen

Journal of Materials Research ◽

10.1557/jmr.2001.0480 ◽

2001 ◽

Vol 16 (12) ◽

pp. 3496-3502 ◽

Cited By ~ 39

Author(s):

Mao Wen ◽

Xue-Jun Xu ◽

Seiji Fukuyama ◽

Kiyoshi Yokogawa

Keyword(s):

Hydrogen Embrittlement ◽

The Body ◽

Embedded Atom Method ◽

Body Centered Cubic ◽

Hydrogen Binding ◽

Hydrogen Trap ◽

Embedded Atom ◽

Bcc Iron ◽

Good Accordance ◽

Embedded Atom Method Potential

A new reliable embedded atom method potential for hydrogen in body-centered-cubic (bcc) iron is developed by fitting not only to the properties of hydrogen in a perfect bcc iron lattice but also to the properties of hydrogen binding to vacancies. The validity of the potential is examined by calculating the properties of hydrogen trap binding to surfaces and dislocations that are in good accordance with the experiments. A brief application of the potential by molecular dynamic simulation reveals that hydrogen accumulated ahead of the crack tip induces serious hydrogen embrittlement.

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Thermal Diffusion and Related Phenomena in Cubic (fcc and bcc) Sulfate Lattices

Zeitschrift für Naturforschung A ◽

10.1515/zna-1968-1225 ◽

1968 ◽

Vol 23 (12) ◽

pp. 2045-2052 ◽

Cited By ~ 3

Author(s):

Arnold Lundén ◽

John-Erik Olsson

Keyword(s):

Thermal Diffusion ◽

High Temperature Phase ◽

Temperature Phase ◽

Face Centered Cubic ◽

Body Centered Cubic ◽

Cold Side ◽

Alkali Ions ◽

Significant Enrichment ◽

Face Centered ◽

Degree Of Order

Thermal diffusion of cations has been studied in face-centered cubic Li2SO4 containing small amounts of other sulfates (temp. range 590—750°C), in body-centered cubic LiAgSO4 containing about 0.5% of other alkali sulfates (450—550°C) and in body-centered cubic LiNaSO4 (546 to 588°C). For the fcc systems the size of the added cation was of great importance for the thermal diffusion. Thus, for the small Na+ and Ag+ ions, the Soret-coefficients (σ) are of the order of only 10-4 degr.-1. The direction has not been established with certatinty, although there are indications that Ag+, and also Ca2+, are enriched on the cold side, while Na+ might be slightly enriched on the hot side. There is a significant enrichment of the large alkali ions (K+, Rb+, Cs+) on the hot side; σ=— 2 × 10-3 degr.-1 for K+. In some experiments with these large alkali ions phase boundaries were intersected, and the large ion was always enriched in the high-temperature phase.In bcc Li2SO4—Ag2SO4 (containing 40 mole % Li2SO4) the light component Li+ was enriched at the hot side: σ ≦ 1.7 × 10-3 degr.-1. Regarding added alkali ions, Na+ is enriched at the hot side (σ ∼ 2 × 10-3 degr.-1), while the direction is not established with certainty for K+ and Rb+. In bcc LiNaSO4 no significant separation of the two cations could be detected, and the Soret-coeffi-cient is certainly less than 10-3 degr.-1.A comparison of fcc and bcc sulfates with molten salts regarding thermal diffusion, electromigration mobility of cations, and the conductivity changes caused by impurities, shows a distinction between the fcc systems on one side and bcc sulfates and melts on the other. This supports previous conclusions that the fcc systems are characterised by a higher degree of order than the bcc ones.

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Temperature and Loading Rate Effect on the Load-Displacement Response of Metal-Metallic Glass (Al-Cu50Zr50) Layered Structure during Nano-Indentation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.978.330 ◽

2020 ◽

Vol 978 ◽

pp. 330-336

Author(s):

Pradeep Gupta ◽

Natraj Yedla

Keyword(s):

Metallic Glass ◽

Loading Rate ◽

Displacement Vector ◽

Peak Load ◽

Md Simulations ◽

Atomic Displacement ◽

Displacement Response ◽

Embedded Atom ◽

Load Displacement ◽

Embedded Atom Method Potential

Molecular dynamics (MD) simulations of metal-metallic glass (Al-Cu50Zr50) multilayer during nanoindentation is carried out to investigate the load-displacement response, mechanical properties and deformation mechanisms. The indentation study is carried out at temperatures in the range of cryogenic to room temperature (10 K-300 K). The indenter speeds are varied between 0.5-5 Å/ps to study the effect of loading rate. The interaction between Al-Cu-Zr atoms are defined by EAM (Embedded Atom Method) potential. A sample size of 200 Å × 200 Å × 200 Å (in x y z-direction) comprising of 538538 atoms is used for nanoindentation. P P S boundary condition (BC) in x y z direction and NVT ensemble are used. We observed a peak load of 117 nN, at a temperature of 10 K with a loading rate of 5 Å/ps. We found that as the loading rate increase, the peak load also increases. As anticipated, the increase in temperature decreases the strength of the multilayer. The atomic displacement vector plots reveal that MG act as hurdles to the movement of dislocations nucleated at the interface.

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A jumping crystal predicted with molecular dynamics and analysed with TLS refinement against powder diffraction data

IUCrJ ◽

10.1107/s205225251801686x ◽

2019 ◽

Vol 6 (1) ◽

pp. 136-144 ◽

Cited By ~ 3

Author(s):

Jacco van de Streek ◽

Edith Alig ◽

Simon Parsons ◽

Liana Vella-Zarb

Keyword(s):

Crystal Structure ◽

Phase Transition ◽

Molecular Dynamics ◽

High Temperature ◽

Md Simulations ◽

High Temperature Phase ◽

Temperature Phase ◽

Powder Diffraction Data ◽

Transition Mechanism ◽

Low Temperature Phase

By running a temperature series of molecular dynamics (MD) simulations starting from the known low-temperature phase, the experimentally observed phase transition in a `jumping crystal' was captured, thereby providing a prediction of the unknown crystal structure of the high-temperature phase and clarifying the phase-transition mechanism. The phase transition is accompanied by a discontinuity in two of the unit-cell parameters. The structure of the high-temperature phase is very similar to that of the low-temperature phase. The anisotropic displacement parameters calculated from the MD simulations readily identified libration as the driving force behind the phase transition. Both the predicted crystal structure and the phase-transition mechanism were verified experimentally using TLS (translation, libration, screw) refinement against X-ray powder diffraction data.

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Molecular Dynamics Simulations Based on Plastic Crystal Model with Introducing United Atom Scheme Demonstrated for Zr2Ni Metallic Glass

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.1337 ◽

2012 ◽

Vol 706-709 ◽

pp. 1337-1342

Author(s):

Akira Takeuchi ◽

Akihisa Inoue

Keyword(s):

Molecular Dynamics ◽

Md Simulations ◽

Simulation Method ◽

Embedded Atom Method ◽

Plastic Crystal ◽

Embedded Atom ◽

Ni Alloy ◽

Crystal Model ◽

Dynamics Simulations ◽

Embedded Atom Method Potential

Molecular dynamics (MD) simulations were performed for a Zr2Ni alloy by referring to crystallographic features of a metastable Zr2Ni phase. Simulation method was identical to our previous studies named plastic crystal model (PCM), which includes crystallographic operations for an intermetallic compound in terms of the random rotations of hypothetical clusters around their center of gravity and subsequent annealing at a low temperature. On the basis of MD-PCM, the present study considers an additional refinement named united atom scheme (UAS) on the motions of atoms in the hypothetical clusters. In MD-PCM-UAS, Dreiding potential was assigned for atomic bonds in a cluster whereas Generalized Embedded Atom Method potential for the other atomic pairs. The simulation results by MD-PCM-UAS yield a liquid-like structure. However, annealing did not cause subsequent structural relaxation, which differs from the results by MD-PCM and conventional MD simulations. Further simulations based on MD-PCM-UAS were performed for a nanostructure comprising clusters and glue atoms, leading to the best fit with the experimental data.

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Formation of high temperature phase in flash-evaporated SnSe films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176629 ◽

1990 ◽

Vol 48 (4) ◽

pp. 698-699

Author(s):

J.P.S. Hanjra

Keyword(s):

Thin Films ◽

Electrical Properties ◽

Energy Gap ◽

Dominant Role ◽

Fine Powder ◽

High Temperature Phase ◽

Temperature Phase ◽

Water Mixture ◽

Flash Evaporation ◽

Photovoltaic Applications

Tin mono selenide (SnSe) with an energy gap of about 1 eV is a potential material for photovoltaic applications. Various authors have studied the structure, electronic and photoelectronic properties of thin films of SnSe grown by various deposition techniques. However, for practical photovoltaic junctions the electrical properties of SnSe films need improvement. We have carried out investigations into the properties of flash evaporated SnSe films. In this paper we report our results on the structure, which plays a dominant role on the electrical properties of thin films by TEM, SEM, and electron diffraction (ED).Thin films of SnSe were deposited by flash evaporation of SnSe fine powder prepared from high purity Sn and Se, onto glass, mica and KCl substrates in a vacuum of 2Ø micro Torr. A 15% HF + 2Ø% HNO3 solution was used to detach SnSe film from the glass and mica substrates whereas the film deposited on KCl substrate was floated over an ethanol water mixture by dissolution of KCl. The floating films were picked up on the grids for their EM analysis.

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