From Brittle to Ductile: A Structure Dependent Ductility of Diamond Nanothread

TL;DR

This study uses molecular dynamics simulations to show that diamond nanothreads can transition from brittle to ductile behavior by adjusting their poly-benzene section length, revealing unique mechanical properties among 1D carbon nanomaterials.

Contribution

It demonstrates the tunable ductility of diamond nanothreads based on their structural length, a novel finding for 1D carbon nanomaterials.

Findings

DNT can switch from brittle to ductile with length variation.

Yield strength is independent of grain size but depends on total length.

Failure is dominated by Stone-Wales defects.

Abstract

As a potential building block for the next generation of devices or multifunctional materials that are spreading almost every technology sector, one-dimensional (1D) carbon nanomaterial has received intensive research interests. Recently, a new ultra-thin diamond nanothread (DNT) has joined this palette, which is a 1D structure with poly-benzene sections connected by Stone-Wales (SW) transformation defects. Using large-scale molecular dynamics simulations, we found that this sp3 bonded DNT can transit from a brittle to a ductile characteristic by varying the length of the poly-benzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropies. Analogously, the SW defects behave like a grain boundary that interrupts the consistency of the poly-benzene sections. For a DNT with a fixed length, the yield strength fluctuates in the vicinity of a certain value and is independent of the "grain size". On the other hand, both yield strength and yield strain show a clear dependence on the total length of DNT, which is due to the fact that the failure of the DNT is dominated by the SW defects. Its highly tunable ductility together with its ultra-light density and high Young's modulus makes diamond nanothread ideal for creation of extremely strong three-dimensional nano-architectures.