Molecular dynamics study of the role of symmetric tilt grain boundaries on the helium distribution in nickel

The role of grain boundaries (GBs) in the diffusion of oxygen vacancies (VO••s) in barium titanate (BaTiO3) and its mechanism were investigated using atomistic simulation techniques. It was found that GBs trapped VO••s at specific sites in the course of the diffusion, and the excess energy reflecting structural distortion of the GB was closely related to the availability of the trapping. GBs therefore act as a resistance of the diffusion of VO••s, suggesting that electrical degradation of multilayer ceramic capacitors (MLCCs), which is derived from vacancy diffusion, enables to be additionally improved by controlling GB structures in BaTiO3-based dielectrics.

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Molecular Dynamics Study of Nonequilibrium [112] Tilt Grain Boundaries in Ni and their Relaxation under Cyclic Deformation

Journal of Metastable and Nanocrystalline Materials ◽

10.4028/www.scientific.net/jmnm.30.1 ◽

2018 ◽

Vol 30 ◽

pp. 1-10

Author(s):

Ayrat A. Nazarov ◽

Ramil’ T. Murzaev

Keyword(s):

Molecular Dynamics ◽

Grain Boundaries ◽

Excess Energy ◽

Stress Fields ◽

Zero Temperature ◽

Partial Lattice ◽

Symmetric Tilt ◽

Nonequilibrium Structure ◽

Calculated Effect ◽

Dynamics Simulations

Atomic structure of nonequilibrium [112] tilt grain boundaries in nickel containing disclination dipoles is studied by means of molecular dynamics simulations. Initial systems for simulations are constructed by joining together pieces of two bicrystals one of which contains a symmetric tilt GB S=11 / 62.96° and the other a GB S=105 / 57.12°, or S=125 / 55.39°, or S=31 / 52.20°, so disclination dipoles with strengths w = 5.84°, 7.58° and 10.76° are created. Stress maps plotted after relaxation at zero temperature indicate the presence of high long-range stresses induced by disclination dipoles. Excess energy of GBs due to the nonequilibrium structure is calculated. Effect of oscillating tension-compression stresses on the nonequilibrium GB structure is studied at temperature T = 300 K. The simulations show that the oscillating stress results in a generation of partial lattice dislocations by the GB, their glide across grains and sink at appropriate surfaces that results in a compensation of the disclination stress fields and recovery of an equilibrium GB structure and energy.

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The Structure, Role and Flexibility of Grain Boundaries

MRS Proceedings ◽

10.1557/proc-1125-r07-38 ◽

2008 ◽

Vol 1125 ◽

Author(s):

M. Samaras ◽

M. Victoria ◽

W. Hoffelner

Keyword(s):

Molecular Dynamics ◽

Grain Boundary ◽

Grain Boundaries ◽

Boundary Movement ◽

Displacement Cascade ◽

Interstitial Atoms ◽

Atomic Analysis ◽

Grain Boundary Movement

ABSTRACTThe structure and role of grain boundaries is investigated using an atomic analysis of the grain boundary movement during Molecular Dynamics displacement cascade simulations of bcc Fe. The results show the grain boundary to be a flexible entity. Local restructuring of the GB accommodates the incoming self interstitial atoms with local kinks, or small movements of a few atomic spacings occurring when the grain boundary is engulfed in the displacement cascade. The damage created is investigated using two potentials: the Ackland (non-magnetic) and the Dudarev- Derlet (magnetic) to study the role and influence of magnetism on the results obtained.

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A Description of Preferential Sites for Vacancy Formation on Grain Boundaries in Copper by Structural Unit Model

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.1351 ◽

2017 ◽

Vol 898 ◽

pp. 1351-1355

Author(s):

Ke Tong ◽

Fei Ye ◽

Ya Kun Wang ◽

Feng Zhou

Keyword(s):

Molecular Dynamics ◽

Grain Boundaries ◽

Structural Unit ◽

Local Stress ◽

Dynamics Simulation ◽

Structural Units ◽

Symmetric Tilt ◽

Unit Model ◽

Large Tensile Stress ◽

Local Stress Field

The preferential sites for vacancies on a series of symmetric tilt grain boundaries in copper have been investigated by molecular dynamics simulation. The regularity of preferential sites for vacancies on these boundaries can be described by the structural unit model. This is essential because of the correspondence between the geometries of the structural units and the local stress field. The vacancies are energetically preferred at the sites with relatively large tensile stress, and these sites are the corner sites of the structural units. Moreover, these preferential sites are mainly related to the structural unit types irrespective of which grain boundary that the structure units locate in. Therefore, the preferential sites for vacancies on various grain boundaries formed by combinations of certain structural units can be readily described and predicted by the structural unit model.

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Molecular dynamics study of UO 2 symmetric tilt grain boundaries around [001] axis

Journal of the American Ceramic Society ◽

10.1111/jace.17736 ◽

2021 ◽

Vol 104 (6) ◽

pp. 2879-2893

Author(s):

Marion Borde ◽

Allan Germain ◽

Emeric Bourasseau

Keyword(s):

Molecular Dynamics ◽

Grain Boundaries ◽

Symmetric Tilt

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Role of CSL Boundaries on Displacement Cascades in β-SiC

MRS Proceedings ◽

10.1557/opl.2013.61 ◽

2013 ◽

Vol 1514 ◽

pp. 43-48

Author(s):

Prithwish K. Nandi ◽

V. Ajay Annamareddy ◽

Jacob Eapen

Keyword(s):

Molecular Dynamics ◽

Grain Boundary ◽

Grain Boundaries ◽

Neutron Irradiation ◽

Md Simulations ◽

Atomic Mobility ◽

Statistical Nature ◽

Displacement Cascades ◽

Tilt Grain Boundary

ABSTRACTMolecular dynamics (MD) simulations are carried out to understand the mechanisms of damage production and recovery near grain boundaries in β-SiC under neutron irradiation. Our investigations show that the damage generated by radiation is reduced by the presence of a ∑9{122}[110] tilt grain boundary. Directional displacements which are averaged over an isoconfigurational ensemble are used to characterize the statistical nature of atomic mobility near the grain boundary.

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