Liu Fu, Wang Qingqing, Tang Yuchao, Du Wan, Chang Weiwei, Fu Zewei, Zhao Xinluo, Liu Yi
Department of Physics, Shanghai University, Shanghai 200444, China.
Materials Genome Institute, Shanghai University, Shanghai 200444, China.
Nanoscale. 2023 Mar 30;15(13):6143-6155. doi: 10.1039/d3nr00386h.
Carbon nanowires (CNWs), long linear carbon chains encapsulated inside carbon nanotubes, exhibit sp hybridization characteristics as one of one-dimensional nanocarbon materials. The research interests on CNWs are accelerated by the successful experimental syntheses from the multi-walled to double-walled until single-walled CNWs recently but the formation mechanisms and structure-property relationships of CNWs remain poorly understood. In this work, we studied the insertion-and-fusion formation process of CNWs at an atomistic level using ReaxFF reactive molecular dynamics (MD) and density functional theory (DFT) calculations with particular focus on the hydrogen (H) adatom effects on the configurations and properties of carbon chains. The constrained MD shows that short carbon chains can be inserted and fused into long carbon chains inside the CNTs due to the van der Waals interactions with little energy barriers. We found that the end-capped H atoms of carbon chains may still remain as adatoms on the fused chains without C-H bond breaking and could transfer along the carbon chains thermal activation. Moreover, the H adatoms were found to have critical effects on the distribution of bond length alternation as well as the energy level gaps and magnetic moments depending on the varied positions of H adatoms on the carbon chains. The results of ReaxFF MD simulations were validated by the DFT calculations and MD simulations. The diameter effect of the CNTs on the binding energies suggest that multiple CNTs with a range of appropriate diameters can be used to stabilize the carbon chains. Different from the terminal H of carbon nanomaterials, this work demonstrated that the H adatoms could be used to tune the electronic and magnetic properties of carbon-based electronic devices, opening up the door toward rich carbon-hydrogen nanoelectronics.
碳纳米线（CNWs）是包裹在碳纳米管内部的长线性碳链，作为一维纳米碳材料之一，具有sp杂化特性。近期，从多壁到双壁直至单壁碳纳米线的成功实验合成加速了对碳纳米线的研究兴趣，但碳纳米线的形成机制及其结构与性能的关系仍知之甚少。在这项工作中，我们使用ReaxFF反应分子动力学（MD）和密度泛函理论（DFT）计算，在原子水平上研究了碳纳米线的插入-融合形成过程，特别关注氢（H）吸附原子对碳链构型和性能的影响。受限分子动力学表明，由于范德华相互作用且能量壁垒较小，短碳链可以插入并融合到碳纳米管内部的长碳链中。我们发现，碳链末端封端的H原子可能仍作为吸附原子保留在融合后的链上，而不会发生C-H键断裂，并且可以通过热激活沿着碳链转移。此外，发现H吸附原子对键长交替的分布以及能级间隙和磁矩具有关键影响，这取决于H吸附原子在碳链上的不同位置。ReaxFF分子动力学模拟的结果通过DFT计算和分子动力学模拟得到了验证。碳纳米管直径对结合能的影响表明，可以使用一系列具有适当直径的多个碳纳米管来稳定碳链。与碳纳米材料的末端H不同，这项工作表明H吸附原子可用于调节碳基电子器件的电子和磁性特性，为丰富的碳-氢纳米电子学打开了大门。
