碳纳米管分子动力学模拟的经验势函数研究

Study on Empirical Potential Energy Function of Molecular Dynamics Simulations for Carbon Nanotubes

针对经验键序势函数没有考虑到碳纳米管原子间长程非键作用的问题,提出了一种新的势函数表达式.该表达式结合了经验键序作用势和雷纳德 琼斯势的特点,能够计算碳原子间的短程相互作用和长程相互作用, 更准确地计算出碳纳米管的原子间作用势能.使用分子动力学模拟方法,研究了单壁碳纳米管原子间的互作用势和杨氏模量.研究结果表明:碳纳米管的单位原子势能随直径的增大而减小,管间作用势能随距离的变化曲线呈U字形,杨氏模量为0 935 TPa左右.模拟计算结果与实验结果和其他理论计算结果吻合得很好,说明改进的势函数模型可准确模拟碳纳米管的力学性质.

Focusing on the problem that the inter-atomic long-range nonbond interaction of carbon nanotubes cannot be represented by the empirical bond order potentials, a novel potential energy expression was presented, combining the reactive empirical bond order potential with Lennard-Jones potential. It can represent the inter-atomic short-range interaction and long-range interaction of carbon, respectively. It also can calculate the inter-atomic interaction potential energies of carbon nanotubes more accurately and more suitable for calculating carbon materials. Based on the extended bond potentials, molecular dynamic simulations are used to study the interaction potential energy of single-walled carbon nanotubes (SWCNTs) and Young's modulus. The results show that the potential energy per atom decreases as the tubular diameters increase. For pairs of tubes, the curve of interaction potential energy against distance shows a U alphabetic shape. The Young's moduli of SWCNTs are about 0.935 TPa. The simulation results accord with existing experiment values and other theoretical values perfectly, which demonstrates that the potential expressions can model the mechanical properties of carbon nanotubes exactly.