Chemomechanics control of tearing paths in graphene

Huang, Xu; Yang, Hui; Duin, Adri C. T. van; Hsia, K. Jimmy; Zhang, Sulin

doi:10.1103/physrevb.85.195453

Cited by 39 publications

(44 citation statements)

References 28 publications

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“…4(e)). In amorphous GeTe, E F is already pinned at the mid-gap by many mechanisms, as reported in previous works [22,28]. Thus, the small number of N-doping-induced gap states does not alter the E F behavior at the mid-gap in the amorphous phases.…”

supporting

confidence: 77%

“…The 2N-doping preserves the valence and reduces the calculation costs for the spin-polarization effect. The presence of germanium vacancies (V Ge ) in combination with N-doping is also examined because V Ge is the most stable native defect in crystalline GeTe [21,22].…”

mentioning

confidence: 99%

“…In As described in the PDOS analysis above, the gap states accordingly reduce the electrical conduction in both r-and o-GeTe. In r-GeTe, which is a crystalline PCM model, E F is pinned at the top of the VB [21,22,28]. Such gap states in crystalline structures act as charge-trapping levels, increasing the electrical resistance of the crystalline phase ( Fig.…”

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confidence: 99%

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Nature of electrical resistivity and structural stability in N-doped GeTe models for reliable phase-change materials

Huang

2014

Phys. Status Solidi B

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We study the effects of nitrogen (N)‐doping on the electrical memory reliability of GeSbTe phase‐change materials based on GeTe prototype models. We find that the loss of secondary bonding (e.g., resonant interlayer bonding) determines the feasibility of various types of N‐doping that can be easily adopted by the GeSbTe system. We give a more generalized explanation beyond compliance with the formation of local Ge3N4 motifs. The nitrogen‐induced change in local order produces crystalline GeTe with shallow states near the valence band edge. These states are localized on the nearest‐neighbor Ge sites, thus reducing the conductivity in the crystalline phase. This trend carries over to c‐GeTe with Ge vacancy. The N‐doped amorphous GeTe models exhibit enhanced degrees of band tail overlap, which pins the Fermi energy in the mid‐gap and thus gives rise to even higher resistivities in the amorphous phases.

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confidence: 77%

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confidence: 99%

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Nature of electrical resistivity and structural stability in N-doped GeTe models for reliable phase-change materials

Huang

2014

Phys. Status Solidi B

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“…The main advantage of this approach in modeling reacting systems is that it often reduces the magnitude of high velocity atoms, which, in turn, provides more stability as changes in bonding occur throughout a simulation. While a majority of ReaxFF studies have used the Berendsen thermostat, others have used the Nose–Hoover thermostat . The Nose–Hoover thermostat scales velocities such that the canonical distribution of velocities is produced for equilibrium systems with moderate thermostat coupling.…”

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confidence: 99%

The effect of time step, thermostat, and strain rate on ReaxFF simulations of mechanical failure in diamond, graphene, and carbon nanotube

2015

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As the sophistication of reactive force fields for molecular modeling continues to increase, their use and applicability has also expanded, sometimes beyond the scope of their original development. Reax Force Field (ReaxFF), for example, was originally developed to model chemical reactions, but is a promising candidate for modeling fracture because of its ability to treat covalent bond cleavage. Performing reliable simulations of a complex process like fracture, however, requires an understanding of the effects that various modeling parameters have on the behavior of the system. This work assesses the effects of time step size, thermostat algorithm and coupling coefficient, and strain rate on the fracture behavior of three carbon-based materials: graphene, diamond, and a carbon nanotube. It is determined that the simulated stress-strain behavior is relatively independent of the thermostat algorithm, so long as coupling coefficients are kept above a certain threshold. Likewise, the stress-strain response of the materials was also independent of the strain rate, if it is kept below a maximum strain rate. Finally, the mechanical properties of the materials predicted by the Chenoweth C/H/O parameterization for ReaxFF are compared with literature values. Some deficiencies in the Chenoweth C/H/O parameterization for predicting mechanical properties of carbon materials are observed.

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“…Reciprocally, local chemical environment and the associated kinetics may also mediate stress generation and mechanical failure of the materials, as exemplified by the hydrogen and lithium (Li) embrittlement [5,6], oxygen-regulated fracture paths in graphene [7], and stress fiber formation in living cells [8]. Such kinetics-stress coupling is universal, but particularly predominant in the electrochemical lithiation of the high-capacity electrode materials, including silicon (Si) and germanium (Ge).…”

mentioning

confidence: 99%