Wang Jian-Tao, Chen Changfeng
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Department of Physics and Astronomy, University of Nevada, Las Vegas, Nevada 89154, USA.
Phys Chem Chem Phys. 2020 Jun 10;22(22):12489-12495. doi: 10.1039/d0cp00834f.
Besides commonly used graphite, carbon nanotubes are also often chosen as precursor materials for the synthesis of new carbon phases. Here we identify, using ab initio calculations, two new three-dimensional crystalline modifications of carbon nanotubes with P63/mcm (D36h) symmetry derived from (6,0) and (9,0) nanotubes via a three-fold distortion assisted reconstruction mechanism. The resulting sp2 + sp3 hybrid network structures have a 24- and 36-atom hexagonal unit cell, termed as (6,0)-hP24 and (9,0)-hP36 carbon, and they topologically correspond to two-dimensional graphyne and graphdiyne. Total-energy calculations show that they are energetically more stable than the original nanotubes and previously reported polymerized nanotube structures. Their dynamic stability has been confirmed by phonon mode analysis. Electronic band structure calculations reveal that they are semiconductors with an indirect band gap of 0.18 eV for hP24, and a direct band gap of 2.15 eV for hP36. The present results establish a new type of carbon phase and offer insights into understanding the complex structural landscape of polymerized nanotubes.
除了常用的石墨外，碳纳米管也常被选作合成新碳相的前驱体材料。在此，我们通过从头算计算，确定了碳纳米管的两种具有P63/mcm（D36h）对称性的新型三维晶体变体，它们是由（6,0）和（9,0）纳米管通过三重畸变辅助重构机制衍生而来的。由此产生的sp2 + sp3杂化网络结构具有24原子和36原子的六边形晶胞，分别称为（6,0）-hP24和（9,0）-hP36碳，它们在拓扑结构上对应于二维石墨炔和石墨二炔。总能计算表明，它们在能量上比原始纳米管和先前报道的聚合纳米管结构更稳定。通过声子模式分析证实了它们的动力学稳定性。电子能带结构计算表明，它们是半导体，hP24的间接带隙为0.18 eV，hP36的直接带隙为2.15 eV。目前的结果建立了一种新型的碳相，并为理解聚合纳米管复杂的结构景观提供了见解。
