Wednesday, 13 October 2004 - 9:00 AM

This presentation is part of : Nano Materials and Material Systems

Stability of nanowires under their own surface stress

Jiankuai Diao, Ken Gall, and Martin L. Dunn. Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309

We performed atomistic simulations to study the effect of free surfaces on the stability of gold nanowires of <100>, <110> and <111> crystallographic orientations. We formed a nanowire by assembling gold atoms into a wire by putting them in their bulk fcc lattice positions. We then relaxed the assemblage to equilibrium. The tensile surface stresses on the sides of the wire cause the wire to contract along the length with respect to the original fcc lattice, and we characterize this deformation in terms of an equilibrium strain versus the cross-sectional area. While the surface stresses cause wires of all sizes and all orientations to increasingly contract with decreasing cross-sectional area, when the cross-sectional area of a [100] nanowire is less than 2.45 nm x 2.45 nm, the wire yields under its own surface stresses, via <112> partial dislocation mechanism. Tensile surface stresses induce compressive stress in the interior of the nanowires and when the compressive stress reaches a critical value, yield occurs. When the nanowire size is less than 1.63 nm x 1.63 nm, reorientation from fcc [100] to fcc [110] occurs, via progressive <112> partial dislocation. This reorientation from fcc <100> to fcc <110> can helps to understand why fcc <110> nanowires are most observed in experiments.

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