[论文解读] A Study on Silicon Nanotubes based on the Tersoff potential

Jeong Won Kang, Jae Jeong Seo+1 more|arXiv (Cornell University)|Oct 2, 2002

Mechanical and Optical Resonators参考文献 1被引用 6

一句话总结

本研究基于Tersoff势的经典分子动力学模拟研究了硅纳米管，结果表明，尽管其结合能高于体相硅，但将石墨烯状片层弯曲成管状所需的弹性能却很低。结果表明，具有混合sp²和sp³杂化的硅纳米管——尤其是sp³成分较高的体系——在能量上更有利，极有可能形成，暗示其存在多壁结构的潜力。

ABSTRACT

This study showed the structures and the thermal behaviors of Si nanocages and nanotubes using classical molecular dynamics simulations based on the Tersoff potential. For hypothetical Si nanotubes based on the Tersoff potential, Si-Si bond length, cohesive energies per atom, diameters, and elastic energy to curve the sheet into tube were in good agreement with those obtained from previous density-functional theory results. Most of the structures, which were obtained from the SA simulations for several initial structures with diamond structure, have included encaged, tubular, or sheet-like structures and have been composed of both sp3 and sp2 bonds. The cohesive energies per atom for silicon nanotubes were higher than that for the Si bulk in the diamond structure, and this implies the difficulty in producing silicon nanotubes or graphitelike sheets. However, since the elastic energy per atom to curve the sheet into tube for silicon atoms is very low, when graphitelike sheets of silicon are formed, the extra cost to produce silicon nanotubes is also very low. When silicon nanotubes are composed of both sp2 and sp3 bonds and the ratio of sp3 to sp2 is high, since the probability of the existence of silicon nanotubes increases, silicon nanotubes similar to multi walled structures are anticipated.

研究动机与目标

• 利用经典分子动力学方法研究硅纳米管的结构稳定性和热行为。
• 评估形成硅纳米管相对于体相金刚石结构硅的能量可行性。
• 评估sp²与sp³杂化在决定硅纳米管稳定性和形成概率中的作用。
• 将模拟结果与先前的密度泛函理论研究结果进行对比，以验证一致性。
• 探索多壁或管状硅纳米结构可能形成的条件。

提出的方法

• 采用基于Tersoff势的经典分子动力学模拟方法，对硅纳米管和纳米笼结构进行建模。
• 使用源自金刚石结构硅的初始构型，通过不同几何形态探索结构演化过程。
• 计算每个原子的结合能，以评估其相对于体相硅的热力学稳定性。
• 量化将二维硅片弯曲成纳米管所需的弹性能，以评估形成成本。
• 分析键合杂化类型（sp²与sp³）及其比例，以理解结构偏好性。
• 将结果与先前的密度泛函理论数据进行对比，验证键长、能量和直径的一致性。

实验结果

研究问题

• RQ1 Tersoff势模拟预测的硅纳米管具有怎样的结构与能量特性？
• RQ2 硅纳米管的结合能与体相金刚石结构硅相比如何？
• RQ3 将二维硅片弯曲成纳米管所需的每个原子的弹性能是多少？
• RQ4 sp²与sp³键合比例如何影响硅纳米管的稳定性和形成概率？
• RQ5 模拟结果与先前密度泛函理论预测的吻合程度如何？

主要发现

• Tersoff势模拟生成了包括包覆型、管状及片状在内的多种结构，其特征为sp²与sp³杂化的混合。
• 硅纳米管的每个原子结合能高于体相金刚石结构硅，表明其在热力学上不利于形成。
• 将二维硅片弯曲成纳米管所需的每个原子弹性能极低，表明弯曲过程的额外能量代价可忽略。
• sp³与sp²键比例较高的硅纳米管表现出更高的形成概率，更倾向于形成稳定、类似多壁结构的形态。
• 模拟得到的键长、直径和结合能与先前密度泛函理论结果高度一致。
• 低弯曲能表明，一旦形成石墨烯状硅片，将其转化为纳米管所需的额外能量极少。