Commun. Comput. Phys., 2 (2007), pp. 451-465.


MD Simulation of Structural and Mechanical Transformation of Single-Walled Carbon Nanotubes Under Pressure

Ji Zang 1, Oswaldo Aldás-Palacios 2, Feng Liu 1*

1 Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, USA.
2 Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, USA. / Visiting Professor, on sabbatical leave from the Escuela Politécnica Nacional, Quito-ECUADOR.

Received 7 July 2006; Accepted (in revised version) 17 August 2006
Communicated by Leihan Tang
Available online 5 October 2006

Abstract

We investigate the structural and mechanical properties of single-walled carbon nanotubes (SWNTs) under hydrostatic pressure, using constant-pressure molecular dynamics (MD) simulations. We observed that all the SWNTs, independent of their size and chirality, behave like a classical elastic ring exhibiting a buckling transition transforming their cross-sectional shape from a circle to an ellipse. The simulated critical transition pressure agrees well with the prediction from continuum mechanics theory, even for the smallest SWNT with a radius of 0.4nm. Accompanying the buckling shape transition, there is a mechanical hardness transition, upon which the radial moduli of the SWNTs decrease by two orders of magnitude. Further increase of pressure will eventually lead to a second transition from an elliptical to a peanut shape. The ratio of the second shape transition pressure over the first one is found to be very close to a constant of $\sim$1.2, independent of the tube size and chirality.


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PACS: 81.07.De, 73.63.Fg, 85.35.Kt
Key words: Carbon nanotube, high-pressure solid-state phase transformation, MD simulation.

*Corresponding author.
Email: zang@eng.utah.edu (J. Zang), oaldas@yahoo.com (O. Aldas-Palacios), fliu@eng.utah.edu (F. Liu)
 

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