Open Access

ABSTRACT

Mechanism study of TiO₂ nanowire tensile behaviors via molecular dynamics simulations

L. Dai¹, V.B.C. Tan^1,2, C.H. Sow^1,3, C.T. Lim^1,2,4, W.C.D. Cheong⁵

1 NUS Nanoscience & Nanotechnology Initiative, National University of Singapore, Singapore
2 Department of Mechanical Engineering, National University of Singapore, Singapore
3 Department of Physics, National University of Singapore, Singapore
4 Division of Bioengineering, National University of Singapore, Singapore
5 Institute of materials Research and Engineering, Singapore

The International Conference on Computational & Experimental Engineering and Sciences 2009, 9(3), 151-162. https://doi.org/10.3970/icces.2009.009.151

Abstract

The mechanisms governing the tensile response of TiO₂ nanowires were studied by molecular dynamics simulations. The free side surfaces of the nanowires were found to be undulating because atoms near the free surface were relaxed into a disordered state during thermodynamic equilibration. For wires below a threshold diameter of around 10 Å, this free surface effect extends throughout the entire wire, resulting in a complete lack of ordered structure. For thick nanowires, the core of the wire retains a crystalline structure. The thicker the wire, the larger the crystalline core and the more dominant is its effect on the tensile behavior of the wire. Under tensile loading, the initial elastic deformation is effected by the reconfiguration of surface atomic bonds. At larger extensions, the structural deformations are accomplished by continuous cycles of Ti-O bond straightening -- bond breakage and inner atomic distortion -- and necking until rupture. The mechanical properties of nanowires are found to be superior to those of bulk TiO₂. Ultra thin nanowires, i.e., those below the threshold diameter, exhibit extraordinarily high stiffness and toughness and are more sensitive to strain rates.

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