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

Abstract

Molecular dynamics (MD) simulations of Cu nanowires at 10 K with varying cross-sectional areas ranging from0.3615 × 0.3615 nm2 to2.169 × 2.169 nm2 have been performed using the embedded atom method (EAM) to investigate theirstructural behaviors and properties at high strain rate. Our studies reported in this papershow the reorientation of square cross-sectional Cu nanowires into a series of stableultra-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 from1 × 109 to0.5 × 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 thepentagonal multi-shell nanobridge structure as compared to structures that do not formsuch a nanobridge. It indicates that the pentagonal nanobridge is stable. The effect ofstrain rate on the mechanical properties of Cu nanowires is also analyzed and shows adecreasing 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 givenstrain 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 giventemperature.