A Reactive Molecular Dynamics Study on the Mechanical Properties of a Recently Synthesized Amorphous Carbon Monolayer Converted into a Nanotube/Nanoscroll

TL;DR

This study uses reactive molecular dynamics to compare the mechanical and thermal properties of amorphous carbon nanotubes and nanoscrolls with their pristine counterparts, revealing the influence of disorder over topology.

Contribution

It provides the first detailed analysis of the mechanical and melting behaviors of amorphous carbon nanotubes and nanoscrolls, highlighting the effects of structural disorder.

Findings

Amorphous structures have lower critical strain thresholds than pristine ones.

Thermal stability of amorphous and pristine structures is similar despite different topologies.

Structural disorder diminishes the influence of topology on mechanical behavior.

Abstract

Recently, laser-assisted chemical vapor deposition was used to synthesize a free-standing, continuous, and stable monolayer amorphous carbon (MAC). MAC is a pure carbon structure composed of randomly distributed five, six, seven, and eight atom rings, which differs from disordered graphene. More recently, amorphous MAC-based nanotubes (a-CNT) and nanoscrolls (A-CNS) were proposed. In this work, we have investigated (through fully atomistic reactive molecular dynamics simulations) the mechanical properties and melting points of pristine and a-CNT and a-CNS. Results showed that a-CNT and a-CNS have distinct elastic properties and fracture patterns concerning their pristine analogs. Both a-CNT and a-CNS presented a non-elastic regime before their total rupture, whereas the CNT and CNS undergo a direct conversion to fractured forms after a critical strain threshold. The critical strain for the fracture of the a-CNT and a-CNS are about 30% and 25%, respectively, and they are lower than the corresponding CNT and CNS cases. Although less resilient to tension, the amorphous tubular structures have similar thermal stability in relation to the pristine cases with melting points of 5500K, 6300K, 5100K, and 5900K for a-CNT, CNT, a-CNS, and CNS, respectively. An interesting result is whereas the behavior of the pristine systems is substantially different depending on the system being a nanotube or a nanoscroll, thus indicating that the topology plays an important role, the same is not true for the amorphous version of the nanostructures, thus indicating that the structural disorder overcomes the topological features.