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arXiv 2210.05045cond-mat.mtrl-scicond-mat.dis-nn
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由随机初始构型形成无定形碳多壁纳米管

Formation of amorphous carbon multi-walled nanotubes from random initial configurations

C. Ugwumadu, R. Thapa, Y. Al-Majali, J. Trembly, D. A. Drabold

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摘要：

从初始随机配置开始并使用高斯近似势[Phys. Rev. B 95，094203（2017）]，模拟了具有多达四个壁和尺寸范围从200到3200个原子的无定形碳纳米管（a-CNT）。成功模拟a-CNTs所需的重要变量（如密度，高度和直径）是用机器学习随机森林技术预测的。采用密度泛函方法对模型进行了$\textit{ex post facto}$验证。a-CNT模型的范围为0.55 nm - 2 nm宽，平均壁间间距为0.31 nm。对a-CNTs中的拓扑缺陷进行了讨论，观察到了新的缺陷构型。讨论了这些相的电子态密度和局域化，并确定了$π$子空间中的离域电子是影响层间凝聚力的重要因素。电子电导率的空间投影有利于沿连接六边形的轴向输运，而网络的非六边形部分阻碍或分叉电子输运。计算了振动态密度，这可能是材料的实验可测试指纹，并讨论了低频径向呼吸模式的出现。使用Green-Kubo公式计算300 K下的热导率。

英文摘要：

Amorphous carbon nanotubes (a-CNT) with up to four walls and sizes ranging from 200 to 3200 atoms have been simulated, starting from initial random configurations and using the Gaussian Approximation Potential [Phys. Rev. B 95, 094203 (2017)]. The important variables (like density, height, and diameter) required to successfully simulate a-CNTs, were predicted with a machine learning random forest technique. The models were validated $\textit{ex post facto}$ using density functional codes. The a-CNT models ranged from 0.55 nm - 2 nm wide with an average inter-wall spacing of 0.31 nm. The topological defects in a-CNTs were discussed and new defect configurations were observed. The electronic density of states and localization in these phases were discussed and delocalized electrons in the $π$ subspace were identified as an important factor for inter-layer cohesion. Spatial projection of the electronic conductivity favors axial transport along connecting hexagons, while non-hexagonal parts of the network either hinder or bifurcate the electronic transport. A vibrational density of states was calculated and is potentially an experimentally testable fingerprint of the material and the appearance of a low-frequency radial breathing mode was discussed. The thermal conductivity at 300 K was calculated using the Green-Kubo formula.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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