Formation of stable ultra-thin pentagon Cu nanowires under high strain rate loading

Abstract

Molecular dynamics (MD) simulations of \langle 100\rangle \mbox {/}{\{}100{\}} Cu nanowires at 10 K with varying cross-sectional areas ranging from 0.3615 × 0.3615 nm2 to 2.169 × 2.169 nm2 have been performed using the embedded atom method (EAM) to investigate their structural behaviors and properties at high strain rate. Our studies reported in this paper show the reorientation of \langle 100\rangle \mbox {/}{\{}100{\}} square cross-sectional Cu nanowires into a series of stable ultra-thin pentagon Cu nanobridge structures with diameter of ~1 nm under a high strain rate tensile loading. The strain rates used for the present studies range from 1 × 109 to 0.5 × 107 s−1. The pentagonal multi-shell nanobridge structure is observed for cross-sectional dimensions <1.5 nm. From these results we anticipate the application of pentagonal Cu nanowires even with diameters of ~1 nm in nano-electronic devices. A much larger plastic deformation is observed in the pentagonal multi-shell nanobridge structure as compared to structures that do not form such a nanobridge. It indicates that the pentagonal nanobridge is stable. The effect of strain rate on the mechanical properties of Cu nanowires is also analyzed and shows a decreasing yield stress and yield strain with decreasing strain rate for a given cross-section. Also, a decreasing yield stress and decreasing yield strain are observed for a given strain rate with increasing cross-sectional area. The elastic modulus is found to be ~100 GPa and is independent of strain rate effect and independent of size effect for a given temperature.