291662 Investigating Length Dependent Failure Modes of Elongating Gold Nanowires Via GPU Computing

Monday, October 29, 2012
Hall B (Convention Center )
Amulya Pervaje1, William R. French1, Christopher R. Iacovella1 and Peter T. Cummings2,3, (1)Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, (2)Center of Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, (3)Chemical & Biomolecular Engineering, Vanderbilt University, Nashville, TN

Elongating gold nanowires are of interest in one regard with their application to molecular electronics.  It has been proposed that the failure mode of metallic nanowires as a result of elongation, either brittle or ductile, depends on the length and diameter of the nanowire, with shorter nanowires having a ductile failure mode and longer nanowires with a brittle failure mode.  The distinction between ductile and brittle failure modes is pinpointed by looking at the stress vs. strain curves of the nanowire as it elongates.  Though this generalized trend has been proposed dividing nanowires based on length and diameter into brittle and ductile failure modes, this trend has previously been based on data from nanowires of fairly large diameters (> 20 nm) and large data samples were not used.  Here we focus on gold nanowires of varying lengths ~3 nm in diameter.  We employ simulations involving GPU computing using HOOMD-Blue with the TB-SMA potential.  From multiple simulations per wire size, we see that there is a gradual transition from ductile to brittle failure modes as gold nanowire length increases.  We further see that the changing stress in the wire correlates with the changing diameter of the wire as it undergoes elongation: in brittle wires a steep drop-off in stress is partnered with a steep drop of in diameter and in ductile wires serrations in the stress/strain curve with stress decreasing more gradually also has diameter decreasing in a more gradual, plateaued manner.  We see a strong relationship between increasing nanowire length and the decreasing strain difference between the failure and yield points of the wire.  This suggests that longer wires break in a more consistent manner with respect to strain and overall elongation.  An interesting phenomenon we observed in our simulations were that some of the longer wires exhibited stress rebounds: after elongating for some time, reaching its yield point, and approaching failure, the stress in the wire cycled through increasing and decreasing stress until eventual failure, manifesting in the wire recoiling in compression and further elongating several times until failure.

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