Lamellar diblock copolymer grain boundary morphology. 1. Twist boundary characterization

1993 ◽  
Vol 26 (17) ◽  
pp. 4506-4520 ◽  
Author(s):  
Samuel P. Gido ◽  
Janelle Gunther ◽  
Edwin L. Thomas ◽  
David Hoffman
Keyword(s):  
Grain Boundary ◽  
Diblock Copolymer ◽  
Twist Boundary

The Properties of a Na-Doped Twist Boundary in SrTiO3 from First Principles

2002 ◽  
Vol 751 ◽  
Author(s):  
Roope K. Astala ◽  
Paul D. Bristowe
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Plane Wave ◽  
First Principles ◽  
Driving Force ◽  
Chemical Potential ◽  
Twist Boundary ◽  
Atomic Displacements ◽  
Formation Energies ◽  
Oxygen Chemical Potential

ABSTRACTThe segregation of Nasr impurities to a Σ = 5 [001] twist boundary in SrTiO3 is studied using DFT-based plane-wave pseudopotential techniques. The formation energies of the impurities are calculated as a function of oxygen chemical potential and electron chemical potential. The results indicate a strong driving force for segregation to the boundary and that the Na impurities exhibit acceptor-like behaviour. The atomic displacements caused by the impurities are small both in the bulk and at the grain boundary. Based on the results a model is suggested in which Nasr segregation is driven by soft relaxation of the electronic structure.

scholarly journals Effects of Grain Boundary Constraint on the Constitutive Response of Tantalum Bicrystals

2003 ◽  
Vol 779 ◽  
Author(s):  
A. Ziegler ◽  
G. H. Campbell ◽  
M. Kumar ◽  
J. S. Stölken
Keyword(s):  
Grain Boundary ◽  
Single Crystals ◽  
Boundary Region ◽  
Twist Boundary ◽  
Compression Tests ◽  
Large Area ◽  
Crystal Rotation ◽  
Boundary Constraint ◽  
Free Region ◽  
Constitutive Response

AbstractThe role of grain boundary constraint in strain localization, slip system activation, slip transmission, and the concomitant constitutive response was examined performing a series of uniaxial compression tests on tantalum bicrystals. Tantalum single crystals were diffusion bonded to form a (011) twist boundary and compressed along the [011] direction. The resulting threedimensional deformation was analyzed via volume reconstruction. With this technique, both the effective states of stress and strain over the cross-sectional area could be measured as a function of distance from the twist boundary, revealing a highly constrained grain boundary region. Post-test metallurgical characterization was performed using Electron Back-Scattered-Diffraction (EBSD) maps. The results, a spatial distribution of slip patterning and mapping of crystal rotation around the twist-boundary, were analyzed and compared to the known behavior of the individual single crystals. A rather large area near the grain boundary revealed no crystal rotation. Instead, patterns of alternating crystal rotation similar to single crystal experiments were found to be some distance away (~1mm) from the immediate grain boundary region, indicating the large length scale of the rotation free region.

Lamellar Diblock Copolymer Grain Boundary Morphology. 4. Tilt Boundaries

1994 ◽  
Vol 27 (21) ◽  
pp. 6137-6144 ◽  
Author(s):  
Samuel P. Gido ◽  
Edwin L. Thomas
Keyword(s):  
Grain Boundary ◽  
Diblock Copolymer ◽  
Tilt Boundaries

scholarly journals Strength of Graphene-Coated Ni Bi-Crystals: A Molecular Dynamics Nano-Indentation Study

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1683
Author(s):  
Vardan Hoviki Vardanyan ◽  
Herbert M. Urbassek
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Composite Structure ◽  
Graphene Layer ◽  
Low Energy ◽  
Twist Boundary ◽  
Interface Failure ◽  
Nano Indentation ◽  
Graphene Composite ◽  
Interface Barrier

Nanoindentation simulations are performed for a Ni(111) bi-crystal, in which the grain boundary is coated by a graphene layer. We study both a weak and a strong interface, realized by a 30 ∘ and a 60 ∘ twist boundary, respectively, and compare our results for the composite also with those of an elemental Ni bi-crystal. We find hardening of the elemental Ni when a strong, i.e., low-energy, grain boundary is introduced, and softening for a weak grain boundary. For the strong grain boundary, the interface barrier strength felt by dislocations upon passing the interface is responsible for the hardening; for the weak grain boundary, confinement of the dislocations results in the weakening. For the Ni-graphene composite, we find in all cases a weakening influence that is caused by the graphene blocking the passage of dislocations and absorbing them. In addition, interface failure occurs when the indenter reaches the graphene, again weakening the composite structure.

scholarly journals Grain Boundary Strength of Molybdenum Bicrystals with a ⟨110⟩ Twist Boundary

1983 ◽  
Vol 47 (7) ◽  
pp. 539-545 ◽  
Author(s):  
Hiroaki Kurishita ◽  
Shunichi Kuba ◽  
Haruyoshi Kubo ◽  
Hideo Yoshinaga
Keyword(s):  
Grain Boundary ◽  
Twist Boundary ◽  
Boundary Strength

Theoretical Investigation of Twist Boundaries in Germanium

1986 ◽  
Vol 77 ◽  
Author(s):  
M. C. Payne ◽  
P. D. Bristowe ◽  
J. D. Joannopoulos
Keyword(s):  
Molecular Dynamics ◽  
Simulated Annealing ◽  
Grain Boundary ◽  
Low Energy ◽  
Energy Structure ◽  
Microscopic Structure ◽  
Twist Boundary ◽  
Small Contraction ◽  
Annealing Method ◽  
Twist Boundaries

ABSTRACTResults of the first completely ab-initio investigation of the microscopic structure of a grain boundary in a semiconductor are presented. Using the molecular dynamics simulated annealing method for performing total energy calculations within the LDA and pseudopotential approximations, the σ=5(001) twist boundary in germanium is studied. A low energy structure is identified which exhibits a rigid body translation and a small contraction at the boundary.

Finite temperature structure and thermodynamics of the Au Σ5 (001) twist boundary

1990 ◽  
Vol 5 (11) ◽  
pp. 2663-2676 ◽  
Author(s):  
R. Najafabadi ◽  
D. J. Srolovitz ◽  
R. LeSar
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Specific Heat ◽  
Excess Volume ◽  
Coefficient Of Thermal Expansion ◽  
Excess Free Energy ◽  
Boundary Structure ◽  
Temperature Structure ◽  
Twist Boundary ◽  
Eam Potential

The structure and thermodynamic properties of a Σ5 (001) twist boundary in gold are studied as a function of temperature. This study was performed within the framework of the Local Harmonic (LH) model and employed an Embedded Atom Method (EAM) potential for gold. We find that for the Σ5 (001) twist boundary in gold, a distorted CSL structure is stable at low temperatures, but undergoes a phase transformation to a DSC related structure near room temperature. This transformation is shown to be first order. The temperature dependences of the excess grain boundary free energy, enthalpy, entropy, specific heat, and excess volume are calculated. Discontinuities are observed in the slope of the grain boundary excess free energy (versus temperature), in the value of the grain boundary excess specific heat and excess volume. The stable high temperature grain boundary structure has a smaller excess volume than does the lower temperature structure, and both structures have a coefficient of thermal expansion which is in excess of that for the perfect crystal.

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