Zhou Xin, Cai Haifang, Hu Chunwei, Shi Jiao, Li Zongli, Cai Kun
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China.
State Key Laboratory of Mechanics and Control of Mechanical Structures and MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
Nanomaterials (Basel). 2020 Apr 28;10(5):846. doi: 10.3390/nano10050846.
A concentric twin tube (CTT) can be built by placing a carbon nanotube (CNT) in another identical CNT. Different from diamondene nanotubes, a stable CTT has no inter-shell covalent bond. As a prestressed double-walled nanotube, CTT has a lower structural stability at a finite temperature. According to the molecular dynamics and first-principle calculations, (a) CTTs have three types of relaxed configurations. In a type III CTT, the inner tube buckles to produce a V-shaped cross-section, and the outer tube may be convex or concave. (b) The minimal radii of relaxed zigzag and armchair CTTs with concave outer tubes were found. (c) After relaxation, the circumferences and areas of the two tubes in a type III CTT are different from those of the corresponding ideal CNT. The area change rate (A-CR) and circumference change rate (C-CR) of the outer tube are the first-order Gaussian function of the radius of the ideal CNT (which forms the CTT), and tends to be 73.3% of A-CR or 95.3% of C-CR, respectively. For the inner tube of a CTT, the A-CR is between 29.3% and 37.0%, and the C-CR is close to 95.8%. (d) The temperature slightly influences the findings given above.
同心双壁碳纳米管（CTT）可以通过将一根碳纳米管（CNT）置于另一根相同的碳纳米管内来构建。与二硼化碳纳米管不同，稳定的CTT没有壳间共价键。作为一种预应力双壁纳米管，CTT在有限温度下具有较低的结构稳定性。根据分子动力学和第一性原理计算，（a）CTT有三种类型的松弛构型。在III型CTT中，内管弯曲形成V形横截面，外管可能是凸的或凹的。（b）发现了具有凹形外管的松弛锯齿形和扶手椅形CTT的最小半径。（c）松弛后，III型CTT中两根碳纳米管的周长和面积与相应理想碳纳米管的不同。外管的面积变化率（A-CR）和周长变化率（C-CR）是形成CTT的理想碳纳米管半径的一阶高斯函数，分别趋于A-CR的73.3%或C-CR的95.3%。对于CTT的内管，A-CR在29.3%至37.0%之间，C-CR接近95.8%。（d）温度对上述结果影响较小。
