关于一种新近合成的可转化为纳米管/纳米卷的无定形碳单层膜力学性能的反应分子动力学研究
A Reactive Molecular Dynamics Study on the Mechanical Properties of a Recently Synthesized Amorphous Carbon Monolayer Converted into a Nanotube/Nanoscroll
AI总结：
本研究通过反应分子动力学模拟，对比了本征与无定形碳纳米管、纳米卷的力学性能和热稳定性，揭示了结构无序对其力学行为和拓扑作用的影响规律。
摘要：
近期，研究人员采用激光辅助化学气相沉积法合成了一种自立式、连续且稳定的单层无定形碳（MAC）。MAC是一种纯碳结构，由随机分布的五元、六元、七元和八元原子环构成，与无序石墨烯有所不同。更近一段时间，基于无定形MAC的纳米管（a-CNT）和纳米卷（a-CNS）被提出。在本研究中，我们通过全原子反应分子动力学模拟，探究了本征型与a-CNT、a-CNS的力学性能和熔点。结果表明，a-CNT和a-CNS与其本征对应物相比，具有截然不同的弹性能和断裂模式。a-CNT和a-CNS在完全断裂前均存在一个非弹性阶段，而本征CNT和CNS在达到临界应变阈值后会直接转变为断裂形态。a-CNT和a-CNS发生断裂的临界应变分别约为30%和25%，均低于对应的本征CNT和CNS的临界应变。尽管无定形管状结构的抗张弹性更弱，但其热稳定性与本征结构相近：a-CNT、CNT、a-CNS和CNS的熔点分别为5500K、6300K、5100K和5900K。一个有趣的结果是：本征体系的行为因体系是纳米管还是纳米卷而存在显著差异，表明拓扑结构发挥着重要作用；而对于无定形版本的纳米结构而言却并非如此，说明结构无序的影响盖过了拓扑特征。
英文摘要：
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.
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