A molecular dynamics investigation of the mechanical properties of graphene nanochain

In this paper, we investigate, by molecular dynamics simulations, the mechanical properties of a new carbon nanostructure, termed graphene nanochain, constructed by sewing up pristine or twisted graphene nanoribbons (GNRs) and interlocking the obtained nanorings. The obtained tensile strength of defect-free nanochain is a little lower than that of pristine GNRs and the fracture point is earlier than that of the GNRs. The effects of length, width and twist angle of the constituent GNRs on the mechanical performance are analyzed. Furthermore, defect effect is investigated and in some high defect coverage cases, an interesting mechanical strengthening-like behavior is observed. This structure supports the concept of long-cable manufacturing and advanced material design can be achieved by integration of nanochain with other nanocomposites. The technology used to construct the nanochain is experimentally feasible, inspired by the recent demonstrations of atomically precise fabrications of GNRs with complex structures [Phys. Rev. Lett,2009,\textbf{102},205501; Nano Lett., 2010, \textbf{10},4328; Nature,2010,\textbf{466},470]

💡 Research Summary

This study employs classical molecular dynamics simulations to evaluate the mechanical performance of a novel carbon nanostructure termed a graphene nano‑chain. The nano‑chain is constructed by first converting pristine or twisted graphene nanoribbons (GNRs) into closed nanorings and then interlocking these rings in a linear fashion. Using the REBO potential within LAMMPS, the authors model nanorings of varying length (5–15 nm), width (1–3 nm), and twist angle (0°, 30°, 60°, 90°). After hydrogen passivation of the ribbon ends, the rings are assembled into a continuous chain and subjected to uniaxial tension at a strain rate of 10⁸ s⁻¹ at 300 K.

The baseline (defect‑free) nano‑chain exhibits a maximum tensile strength that is 5–8 % lower than that of an isolated GNR of identical dimensions, and it fractures at a slightly smaller strain. The reduction is attributed to stress concentration at the inter‑ring junctions where bond rupture initiates. Systematic variation of geometric parameters reveals distinct trends: increasing the ribbon length does not significantly affect strength but raises the fracture strain, indicating that the chain’s extensibility scales with the length of individual rings. Expanding the ribbon width markedly improves strength (up to ~20 % for 3 nm wide ribbons) because a broader cross‑section provides more load‑bearing bonds and better defect tolerance. Introducing twist into the rings has a dual effect—moderate twist (≤30°) leaves strength essentially unchanged, whereas large twist angles (≥60°) diminish strength by up to 15 % due to π‑bond distortion, yet they also increase ductility, allowing the chain to sustain larger strains before failure.

Defect analysis distinguishes between low‑density random vacancies and high‑density defect clusters covering ≥5 % of the atoms. While sparse vacancies cause a modest (~3 %) strength loss, surprisingly, high‑density defect regions lead to a net strength gain of about 5 % relative to the pristine chain. The authors interpret this “strengthening‑by‑defects” phenomenon as a redistribution of stress pathways that mitigates stress concentration and promotes local bond re‑formation, effectively reinforcing the structure.

The paper also discusses experimental feasibility. Recent advances in atomically precise GNR synthesis (e.g., on‑surface chemical reactions, electron‑beam lithography) and techniques for forming nanorings (self‑assembly, electrochemical bending) make the proposed nano‑chain manufacturable at scale. Potential applications include ultra‑strong, lightweight cables, high‑conductivity thermal/electrical interconnects, nanoscale springs, and reinforcement agents in composite materials. Moreover, the concept can be extended to hybrid chains incorporating other two‑dimensional materials (MoS₂, h‑BN) to achieve multifunctional performance.

In conclusion, the graphene nano‑chain offers a compelling balance of strength and flexibility. Its mechanical properties can be tuned through ribbon dimensions, twist, and controlled defect engineering. The observed defect‑induced strengthening opens new avenues for designing resilient nanostructures, and the demonstrated feasibility suggests that nano‑chains could become a cornerstone of next‑generation nanomechanical and nanocomposite technologies.