Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate

ABSTRACTYtterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such applications, the transport of oxygen and water vapor through these coatings to the ceramic substrate is undesirable if high temperature oxidation is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated and interstitial oxygen diffusion in Ytterbium disilicate. Oxygen vacancy and interstitial site energies, vacancy and interstitial formation energies, and migration barrier energies were computed using Density Functional Theory. We have found that, in the case of vacancy-mediated diffusion, many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small. In the case of interstitial diffusion, migration barrier energies are typically around one electron volt, but the interstitial defect formation energies are positive, with the result that the disilicate is unlikely to exhibit experience significant oxygen permeability except at very high temperature.

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“Order-Order” Kinetics in Triple-Defect B2-Ordered Binary Intermetallics: Kinetic Monte Carlo Simulation

Diffusion Foundations ◽

10.4028/www.scientific.net/df.2.191 ◽

2014 ◽

Vol 2 ◽

pp. 191-220 ◽

Cited By ~ 1

Author(s):

A. Biborski ◽

Rafal Abdank-Kozubski ◽

V. Pierron-Bohnes

Keyword(s):

Monte Carlo ◽

Defect Formation ◽

Vacancy Concentration ◽

Kinetic Monte Carlo ◽

Pair Interaction ◽

Simulated System ◽

Antisite Defects ◽

Formation Energies

Triple-defect formation in B2-ordered binary A-B intermetallic compounds results fromthe asymmetry between the formation energies of A- and B-antisite defects. Chemical disorderingin such systems is strictly correlated with vacancy formation, which is the reason for usually veryhigh vacancy concentration. Consequently, Kinetic Monte Carlo (KMC) simulation of processes occurringin the triple-defect systems and controlled by atomic migration via vacancy mechanism mustinvolve complete vacancy thermodynamics – i.e. the simulated system must contain the equilibriumtemperature-dependent number of vacancies. The fully consistent approach based on two differentMonte Carlo techniques has been applied in the present study. The AB intermetallic was modelled withan Ising-type Hamiltonian and KMC simulated for “order-order” kinetics with temperature-dependentequilibrium number of vacancies previously determined by means of Semi Grand Canonical MonteCarlo (SGCMC) simulations. The procedure required in addition the determination of saddle -pointenergies assigned to particular atomic jumps to nn vacancies. Their values were estimated in relationto the nn pair-interaction energies with reference to Molecular Statics simulations performed for NiAlsystem with EAM energetics. The results elucidated the role of triple-defect formation as the atomisticscaleorigin of the experimentally observed surprisingly low rate of the “order-order” kinetics in bulkNiAl.

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Coalescence of the Fullerenes in SWNT with Bend Junction

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.697.789 ◽

2016 ◽

Vol 697 ◽

pp. 789-794

Author(s):

Kai Zhang ◽

Zi Wei Xu ◽

Feng Ding ◽

Gui Wu Liu ◽

Guan Jun Qiao

Keyword(s):

Monte Carlo ◽

Carbon Nanotube ◽

Kinetic Monte Carlo ◽

Chiral Angle ◽

Single Walled Carbon Nanotube ◽

Single Walled Carbon ◽

Lower Productivity ◽

Two Sides ◽

Formation Energies ◽

Specific Control

The coalescence of the fullerenes encapsulated in the host single-walled carbon nanotube (SWNT) with bend junction is explored theoretically by energy driven kinetic Monte Carlo (EDKMC) method. Despite the lower productivity of successful coalescence (with clear identified chiralitys), there is still a possibility to form the inner tube with bend junction which can copy the separated pentagon and heptagon from the host tube exactly with the chiralitys at the two sides clearly identified. The statistic to ~20 successfully coalesced inner tubes with bend junctions shows that the chiral angle differences (CAD) between the two sides > 20 o, which is determined by the minimization of the formation energies of the junctions. Therefore, the chirality distribution of the inner tube may be effectively narrowed by tuning the CAD of the bend host tube, which may provide an alternative way to the application of specific control to the chiralitys.

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A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

Physical Chemistry Chemical Physics ◽

10.1039/d1cp03394h ◽

2021 ◽

Author(s):

Shehab Shousha ◽

Sarah Khalil ◽

Mostafa Youssef

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Defect Formation ◽

Defect Chemistry ◽

Cation Diffusion ◽

Functional Theory ◽

Migration Barriers ◽

Hubbard U ◽

And Migration ◽

Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

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Migration of Zeolite-Encapsulated Pt and Au Under Reducing Atmospheres

10.26434/chemrxiv.14456316.v1 ◽

2021 ◽

Author(s):

Dianwei Hou ◽

Christopher Heard

Keyword(s):

Monte Carlo ◽

Potential Energy Surfaces ◽

Density Functional ◽

Noble Metals ◽

Kinetic Monte Carlo ◽

Pore System ◽

Kinetic Monte Carlo Simulations ◽

Zeolite Lta ◽

Metal Migration ◽

Energy Surfaces

Unbiased density functional global optimisation calculations, followed by kinetic Monte Carlo simulations are used to enumerate the potential energy surfaces for migration of noble metals Pt and Au inside the pore system of siliceous zeolite LTA. The effects of reducing adsorbates CO and H2 are determined. It is found that the two metals differ significantly in the strength and type of interaction with the framework, with strong, framework breaking interactions between Pt and and the zeolite, but only weak dispersive interactions between Au and the zeolite. Adsorbates are found to dramatically interfere with Pt-framework binding, leading to poorer atom-trapping, enhanced metal migration and faster equilibration.

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Enhanced nucleation of Al islands on H-dosed Si(100)-2×1 surface: A combined density functional theory and kinetic Monte Carlo study

Surface Science ◽

10.1016/j.susc.2013.07.003 ◽

2013 ◽

Vol 617 ◽

pp. 73-80 ◽

Cited By ~ 4

Author(s):

Marvin A. Albao ◽

Darwin B. Putungan ◽

Chia-Hsiu Hsu ◽

Feng-Chuan Chuang

Keyword(s):

Density Functional Theory ◽

Monte Carlo ◽

Density Functional ◽

Kinetic Monte Carlo ◽

Monte Carlo Study ◽

Functional Theory

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Computational study of Mg insertion into amorphous silicon: advantageous energetics over crystalline silicon for Mg storage

MRS Proceedings ◽

10.1557/opl.2013.1036 ◽

2013 ◽

Vol 1540 ◽

Cited By ~ 1

Author(s):

Fleur Legrain ◽

Oleksandr I. Malyi ◽

Teck L. Tan ◽

Sergei Manzhos

Keyword(s):

Density Functional ◽

Nearest Neighbor ◽

Defect Formation ◽

Crystalline Silicon ◽

Computational Study ◽

Binding Energies ◽

Functional Theory ◽

Wide Range ◽

Insertion Sites ◽

Formation Energies

ABSTRACTWe show in a theoretical density functional theory study that amorphous Si (a-Si) has more favorable energetics for Mg storage compared to crystalline Si (c-Si). Specifically, Mg and Li insertion is compared in a model a-Si simulation cell. Multiple sites for Mg insertion with a wide range of binding energies are identified. For many sites, Mg defect formation energies are negative, whereas they are positive in c-Si. Moreover, while clustering in c-Si destabilizes the insertion sites (by about 0.1/0.2 eV per atom for nearest-neighbor Li/Mg), it is found to stabilize some of the insertion sites for both Li (by up to 0.27 eV) and Mg (by up to 0.35 eV) in a-Si. This could have significant implications on the performance of Si anodes in Mg batteries.

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Tem Observation Of Grown-In Defects In CZ-Si Crystals And Their Secco Etching Properties

MRS Proceedings ◽

10.1557/proc-442-119 ◽

1996 ◽

Vol 442 ◽

Cited By ~ 5

Author(s):

Masahiro Kato ◽

Hiroshi Takeno ◽

Yutaka Kitagawara

Keyword(s):

High Temperature ◽

High Temperature Oxidation ◽

Defect Formation ◽

Flow Patterns ◽

Dislocation Loops ◽

Formation Factor ◽

Total Size ◽

Laser Scattering ◽

Temperature Oxidation ◽

Defect Species

AbstractGrown-in defects detected by IR laser scattering tomography (LSTDs) in Czochralski-grown Si crystals were identified by transmission electron microscopy (TEM) with a special defect positioning technique. The basic structure of the LSTD was revealed to be a composite of two or three incomplete octahedral voids with the 100–300nm total size. The TEM images of the defect showed existence of 2∼4nm-thick walls surrounding the voids. These thin-walls are considered to be made of oxide, SiOx. These LSTDs are indeed dominant grown-in defect species in most of the commercial CZ-Si walers. The LSTD after 1200°C oxidation was also observed by TEM. The resulting image shows that the defect changed from void to filled oxide precipitate by the high temperature heat treatment. On the other hand, in very slowly pulled crystals with ∼0.4mm/min rate, interstitial type dislocation loops were observed as major defect species. Non-agitated Secco etching of these grown-in defects delineates “flow patterns” (FPs) or pits without the flow patterns. The FP forming property is shown to disappear by oxidation at temperature above 1150°C, while the defect itself remains stable. This implies that the grown-in defects lose their chemical properties to form FPs by the high-temperature oxidation. It is further revealed that the grown-in defects, which once lost the FP forming property by the high-temperature oxidation, can form FPs again by an intentional Cu contamination. Thus a possible FP formation factor is Cu decoration at the grown-in defect site. Defect formation model of the as-grown twin-type LSTD is also proposed.

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Density-functional calculations of defect formation energies using the supercell method: Brillouin-zone sampling

Physical Review B ◽

10.1103/physrevb.71.245204 ◽

2005 ◽

Vol 71 (24) ◽

Cited By ~ 23

Author(s):

Jihye Shim ◽

Eok-Kyun Lee ◽

Young Joo Lee ◽

Risto M. Nieminen

Keyword(s):

Brillouin Zone ◽

Density Functional Calculations ◽

Density Functional ◽

Defect Formation ◽

Zone Sampling ◽

Formation Energies

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Diffusion in Ni-Based Single Crystal Superalloys with Density Functional Theory and Kinetic Monte Carlo Method

Communications in Computational Physics ◽

10.4208/cicp.111115.271115a ◽

2016 ◽

Vol 20 (3) ◽

pp. 603-618 ◽

Cited By ~ 6

Author(s):

Min Sun ◽

Zi Li ◽

Guo-Zhen Zhu ◽

Wen-Qing Liu ◽

Shao-Hua Liu ◽

...

Keyword(s):

Density Functional Theory ◽

Monte Carlo ◽

Transition Rate ◽

Density Functional ◽

Diffusion Theory ◽

Kinetic Monte Carlo ◽

Functional Theory ◽

Atom Diffusion ◽

Time Stepping ◽

Phase Intermetallic

AbstractIn the paper, we focus on atom diffusion behavior in Ni-based superalloys, which have important applications in the aero-industry. Specifically, the expressions of the key physical parameter – transition rate (jump rate) in the diffusion can be given from the diffusion theory in solids and the kinetic Monte Carlo (KMC) method, respectively. The transition rate controls the diffusion process and is directly related to the energy of vacancy formation and the energy of migration of atom from density functional theory (DFT). Moreover, from the KMC calculations, the diffusion coefficients for Ni and Al atoms in the γ phase (Ni matrix) and the γʹ phase (intermetallic compound Ni3Al) of the superalloy have been obtained. We propose a strategy of time stepping to deal with the multi-time scale issues. In addition, the influence of temperature and Al concentration on diffusion in dilute alloys is also reported.

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