Structural complexity in grain boundaries with covalent bonding

Tarnow, Eugen; Dallot, P.; Bristowe, Paul D.; Joannopoulos, John D.; Francis, G. P.; Payne, M. C.

doi:10.1103/physrevb.42.3644

Cited by 66 publications

(22 citation statements)

References 35 publications

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“…In this case, bond distortion and the presence of dangling bonds have the potential to generate electronic states in the band gap since these effects tend to diminish or vanish the splitting between the bonding and antibonding states. In practice, it has been reported that bond disorder induces highly localized electronic states around the top of the valence band and the bottom of the conduction band for tilt and twist boundaries in Si, Ge, and SiC, 62,[68][69][70][71] and that such electronic states can be deep in the band gap when bond distortion is large and/or dangling bonds are present. [68][69][70][71] For ZnO, its ionicity should make the valence and conduction bands consist of the interactions among like atoms in addition to the interactions between Zn and O atoms.…”

Section: B Electronic Structurementioning

confidence: 99%

“…In practice, it has been reported that bond disorder induces highly localized electronic states around the top of the valence band and the bottom of the conduction band for tilt and twist boundaries in Si, Ge, and SiC, 62,[68][69][70][71] and that such electronic states can be deep in the band gap when bond distortion is large and/or dangling bonds are present. [68][69][70][71] For ZnO, its ionicity should make the valence and conduction bands consist of the interactions among like atoms in addition to the interactions between Zn and O atoms. If the former feature dominates, bond distortion and the presence of dangling bonds do not necessarily induce electronic states in the band gap: the localized electronic states associated with the bond disorder should tend to form within the valence or conduction band.…”

Section: B Electronic Structurementioning

confidence: 99%

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Ab initiostudy of symmetric tilt boundaries in ZnO

et al. 2001

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The atomic and electronic structure of the ͓0001͔/(1 2 3 0) ⌺ϭ7 symmetric tilt boundary in ZnO has been investigated by an ab initio plane-wave pseudopotential method within the local-density approximation. Two types of equilibrium geometries are obtained with similar boundary energies. Atomic arrangement is largely reconstructed to vanish dangling bonds in one configuration, whereas the other shows small bond distortion but has dangling bonds at the boundary core. The balance between the energies for deforming atomic arrangements and vanishing dangling bonds should be significant in determining the boundary energies. The electronic structure of the grain boundaries is discussed with a special interest in the relationship with the bond disorder. Owing to the bond distortion and/or the presence of the dangling bonds, localized states form mainly at the lower valence band and the bottom of the upper valence band. On the other hand, the electronic states in the vicinity of the band gap are not significantly affected by the bond disorder. Deep electronic states are not generated in the band gap even for the configuration with dangling bonds. This behavior can be generally explained by the band structure intrinsic to ZnO.

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Section: B Electronic Structurementioning

confidence: 99%

Section: B Electronic Structurementioning

confidence: 99%

Ab initiostudy of symmetric tilt boundaries in ZnO

et al. 2001

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“…The existence of the large number of energy minima found in our simulations for a low-angle shear boundary resembles the phenomenon Energy of the supercell (with respect to the minimum energy structure) with a shear boundary depending on an atomic configuration of the intersection S2. In the column for coordination defects, the numbers of three-coordinated (dangling bond (DB)) or five-coordinated defects (floating bond (FB)) defects in the intersection are listed previously reported for a high-angle (001) S 5 twist boundary in Ge [16] and Si [17]. However, in the last case the degeneracy was associated with different translational states of the twist boundary.…”

Section: Discussion Of Resultsmentioning

confidence: 95%

Extended Point Defect Structures at Intersections of Screw Dislocations in Si: A Molecular Dynamics Study

Belov

Scheerschmidt

Gösele

1999

phys. stat. sol. (a)

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Molecular dynamics computer simulations have been employed with the Tersoff interatomic potential to examine the atomic structure of (aa2) h110i screw dislocations forming regular two-dimensional arrays in silicon. The main attention is focused on the atomic configurations of dislocation intersections. The dislocations are assumed to be undissociated, following HREM observations on the low-angle (001) twist boundaries produced by silicon wafer bonding in ultrahigh vacuum. It is shown that cores of the dislocation intersections are formed by closed characteristic groups of atoms (extended point defects). The symmetry of these defects strongly depends on the fact whether the screw dislocation arrays generate a twist or a shear boundary.

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“…The ability of this method to describe the energetics and thermodynamics at finite temperatures when coupled with Monte Carlo techniques has been demonstrated in Refs. [21][22][23][24]. The crux of the effective Hamiltonian method is to perform the computations over a reduced set of degrees of freedom associated with the system under investigation.…”

Section: Effective Grain Boundary Hamiltonianmentioning

confidence: 99%

Structure and energetics of long-period tilt grain boundaries using an effective Hamiltonian

2001

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We have investigated the atomic structures of 44 ͗110͘ symmetric tilt grain boundaries ͑GB's͒ with atomistic simulations using an embedded-atom method ͑EAM͒ potential for aluminum. The focus has been on examining the efficacy of the structural unit model in the context of very long period boundaries. Our studies, which have been carried out using two EAM potentials, of both the equilibrium and metastable structures of a number of boundaries, reveal that geometric arguments inherent in the structural unit model must be supplemented by energetic considerations. An effective Hamiltonian is introduced to this end which computes the energy of a string of structural units using two-body potentials between individual units. The potentials are calculated via a least-squares fit to the results of full atomistic represented by the effective Hamiltonian. Results based on as few as 16 inputs are very encouraging and clearly demonstrate the effectiveness of this method. This scheme lends itself to a straightforward extension to GB structure calculations at finite temperatures using Monte Carlo techniques.

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Structural complexity in grain boundaries with covalent bonding

Cited by 66 publications

References 35 publications

Ab initiostudy of symmetric tilt boundaries in ZnO

Ab initiostudy of symmetric tilt boundaries in ZnO

Extended Point Defect Structures at Intersections of Screw Dislocations in Si: A Molecular Dynamics Study

Structure and energetics of long-period tilt grain boundaries using an effective Hamiltonian

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