Geometrical considerations concerning the structural irregularities to be assumed in a crystal

We introduce a model for amorphous grain boundaries in graphene and find that stable structures can exist along the boundary that are responsible for local density of states enhancements both at zero and finite ͑ϳ0.5 eV͒ energies. Such zero-energy peaks, in particular, were identified in STS measurements ͓J. Červenka, M. I. Katsnelson, and C. F. J. Flipse, Nat. Phys. 5, 840 ͑2009͔͒ but are not present in the simplest pentagonheptagon dislocation array model ͓O. V. Yazyev and S. G. Louie, Phys. Rev. B 81, 195420 ͑2010͔͒. We consider the low-energy continuum theory of arrays of dislocations in graphene and show that it predicts localized zero-energy states. Since the continuum theory is based on an idealized lattice scale physics it is a priori not literally applicable. However, we identify stable dislocation cores, different from the pentagonheptagon pairs that do carry zero-energy states. These might be responsible for the enhanced magnetism seen experimentally at graphite grain boundaries.

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“…[13][14][15] In this section we make observations relevant to such models in graphene, inspired by the recent STM experiments.…”

Section: Dislocations In Graphene As Base Of Grain Boundary Modelsmentioning

confidence: 99%

Electronic states of graphene grain boundaries

et al. 2010

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“…Historically, research has focused on developing a method to characterize grain boundaries [12][13][14][15][16][17] and their influence on the physical properties of polycrystalline materials. These models utilize dislocation arrays, disclinations, and coincident site lattice (CSL) to describe the local structure of grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Energetics of vacancy segregation to symmetric tilt grain boundaries in hexagonal closed pack materials

Bhatia

Solanki

2013

Journal of Applied Physics

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Molecular static simulations of 190 symmetric tilt grain boundaries in HCP metals were used to understand the energetics of vacancy segregation, which is important for designing stable interfaces in harsh environments. Simulation results show that the local arrangements of grain boundaries and the resulting structural units have a significant influence on the magnitude of vacancy binding energies, and the site-to-site variation within each boundary is substantial. Comparing the vacancy binding energies for each site in different c/a ratio materials shows that the binding energy increases significantly with an increase in c/a ratio. For example, in the 12 10 tilt axis, Ti and Zr with c/a=1.5811 have a lower vacancy binding energy than the Mg with c/a=1.6299. Furthermore, when the grain boundary energies of all 190 boundaries in all three elements are plotted against the vacancy binding energies of the same boundaries, a highly negative correlation (r = -0.7144) is revealed that has a linear fit with a proportionality constant of -25 Å 2 . This is significant for applications where extreme environmental damage generates lattice defects and grain boundaries act as sinks for both vacancies and interstitial atoms.

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“…The edge dislocation, introduced by Orowan (1934), Polanyi (1934), and Taylor (1934aTaylor ( , 1934b, is represented by the line ℓ along which the vectors and are perpendicular. If the vectors and are parallel, then the corresponding dislocation is called a screw dislocation (Burgers, 1939(Burgers, , 1940. In many materials, dislocations are found where the line direction and are neither perpendicular nor parallel and these dislocations are called mixed dislocations, consisting of both edge and screw character.…”

Section: Introductionmentioning

confidence: 99%