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Observation of the smallest metal nanotube with a square cross-section


Understanding the mechanical properties of nanoscale systems requires a range of measurement techniques and theoretical approaches to gather the relevant physical and chemical information. The arrangements of atoms in nanostructures and macroscopic matter can be different, principally due to the role of surface energy, but the interplay between atomic and electronic structure in association with applied mechanical stress can also lead to surprising differences. For example, metastable structures such as suspended chains of atoms1,2,3 and helical wires4,5 have been produced by stretching metal junctions. Here, we report the spontaneous formation of the smallest possible metal nanotube with a square cross-section during the elongation of silver nanocontacts. Ab initio calculations and molecular simulations indicate that the hollow wire forms because this configuration allows the surface energy to be minimized, and also generates a soft structure capable of absorbing a huge tensile deformation.

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Figure 1: Elongation of a silver nanowire along the [001] axis.
Figure 2: Structure of silver nanowires.
Figure 3: Apparent nanowire axial rotation.
Figure 4: Theoretical analysis of the derived atomic wire structures.


  1. Onishi, H., Kondo, Y. & Takayanagi, K. Quantized conductance through individual rows of suspended gold atoms. Nature 395, 780–783 (1998).

    Article  Google Scholar 

  2. Yanson, A. I., Bollinger, G. R., van den Brom, H. E., Agrait, N. & van Ruitenbeek, J. M. Formation and manipulation of a metallic wire of single gold atoms. Nature 395, 783–785 (1998).

    Article  CAS  Google Scholar 

  3. Rodrigues, V. & Ugarte, D. Real-time imaging of atomistic process in one-atom-thick metal junctions. Phys. Rev. B 63, 073405 (2001).

    Article  Google Scholar 

  4. Kondo, Y. & Takayanagi, K. Synthesis and characterization of helical multi-shell gold nanowires. Science 289, 606–608 (2000).

    Article  CAS  Google Scholar 

  5. Gülseren, O., Ercolessi, F. & Tosatti, E. Noncrystalline structures of ultrathin unsupported nanowires. Phys. Rev. Lett. 80, 3775–3778 (1998).

    Article  Google Scholar 

  6. Agraït, N., Yeyati, A. L. & van Ruitenbeek, J. M. Quantum properties of atomic-sized conductors. Phys. Rep. 377, 81–279 (2003).

    Article  Google Scholar 

  7. Marks, L. D. Experimental studies of small-particle structures. Rep. Prog. Phys. 57, 603–649 (1994).

    Article  CAS  Google Scholar 

  8. Rodrigues, V., Bettini, J., Rocha, A. R., Rego, L. G. C. & Ugarte, D. Quantum conductance in silver nanowires: Correlation between atomic structure and transport properties. Phys. Rev. B 65, 153402 (2002).

    Article  Google Scholar 

  9. Rodrigues, V., Fuhrer, T. & Ugarte, D. Signature of atomic structure in the quantum conductance of gold nanowires. Phys. Rev. Lett. 85, 4124–4127 (2000).

    Article  CAS  Google Scholar 

  10. Bettini, J., Rodrigues, V., González, J. C. & Ugarte, D. Real-time atomic resolution study of metal nanowires. Appl. Phys. A 81, 1513–1518 (2005).

    Article  CAS  Google Scholar 

  11. González, J. C. et al. Indication of unusual pentagonal structures in atomic-size Cu nanowires. Phys. Rev. Lett. 93, 126103 (2004).

    Article  Google Scholar 

  12. Bettini, J. et al. Experimental realization of suspended atomic chains composed of different atomic species. Nature Nanotech. 1, 182–185 (2006).

    Article  CAS  Google Scholar 

  13. Sanchez-Portal, D., Ordejón, P., Artacho, E. & Soler, J. M. Density-functional method for very large systems with LCAO basis sets. Int. J. Quantum Chem. 65, 453–461 (1997).

    Article  Google Scholar 

  14. Soler, J. M. et al. The SIESTA method for ab initio order-N materials simulation. J. Phys.: Condens. Matter 14, 2745–2779 (2002).

    CAS  Google Scholar 

  15. Cheng, D., Kim, W. Y., Min, S. K., Nautiyal, T. & Kim, K. S. Magic structures and quantum conductance of [110] silver nanowires. Phys. Rev. Lett. 96, 096104 (2006).

    Article  Google Scholar 

  16. Jia, J., Shi, D., Zhao, J. & Wang, B. Structural properties of silver nanowires from atomistic descriptions. Phys. Rev. B 76, 165420 (2007).

    Article  Google Scholar 

  17. Rego, L. G. C., Rocha, A. R., Rodrigues, V. & Ugarte, D. Role of structural evolution in the quantum conductance behavior of gold nanowires during stretching. Phys. Rev. B 67, 165420 (2003).

    Article  Google Scholar 

  18. Kondo, Y. & Takayanagi, K. Gold nanobridge stabilized by surface structure. Phys. Rev. Lett. 79, 3455–3458 (1997).

    Article  CAS  Google Scholar 

  19. Oshima, Y., Onga, A. & Takayanagi, K. Helical gold nanotube synthesized at 150 K. Phys. Rev. Lett. 91, 205503 (2003).

    Article  Google Scholar 

  20. Lagos, M., Rodrigues, V. & Ugarte, D. Structural and electronic properties of atomic-size wires at low temperatures. J. Electron Spectrosc. Rel. Phenom. 156, 20–24 (2007).

    Article  Google Scholar 

  21. Perdew, J. P. & Zunger, A. Self-interaction correction to density-functional approximations for many-electron systems. Phys. Rev. B 23, 5048–5079 (1981).

    Article  CAS  Google Scholar 

  22. Troullier, N. & Martins, J. L. Efficient pseudopotentials for plane-wave calculations. Phys. Rev. B 43, 1993–2006 (1991).

    Article  CAS  Google Scholar 

  23. Rodrigues, V., Sato, F., Galvão, D. S. & Ugarte, D. Size limit of defect formation in pyramidal Pt nanocontacts. Phys. Rev. Lett. 99, 255501 (2007).

    Article  CAS  Google Scholar 

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P.C. Silva is acknowledged for assistance during sample preparation. This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).

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M.J.L., J.B., V.R. and D.U. were responsible for the experimental work. F.S. and D.S.G. performed the theoretical calculations. All authors discussed the results and commented on the manuscript.

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Correspondence to D. Ugarte.

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Lagos, M., Sato, F., Bettini, J. et al. Observation of the smallest metal nanotube with a square cross-section. Nature Nanotech 4, 149–152 (2009).

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