單壁奈米碳管機械性質之分子動力學模擬

Abstract

奈米碳管為二十一世紀的新興材料，逐漸被人們利用於各種高科技或是民生用品之中，所以對奈米碳管的機械性質的了解對奈米碳管的應用有十分大的幫助。本論文利用分子動力學模擬來計算單壁奈米碳管的機械性質與力學行為，採用Tersoff 勢能來表示碳管內碳原子的交互作用，於固定粒子數、固定體積及溫度的情況下開始模擬，模擬單壁奈米碳管拉伸、壓縮及扭轉的行為並利用其能量與應變的關係求得所要之楊氏模數與剪力模數。本文內有兩種方式比較碳管的機械性質，一固定直徑，改變碳管半徑，另一種為改變碳管長度，固定半徑的方式下去模擬並計算其機械性質，比較其結果。而單壁奈米碳管所求的之楊氏模數為0.613 Tpa，而剪力模數為0.396 Tpa，而透過幾何形狀的改變，楊氏模數並無一定的趨勢，而剪力模數會隨著碳管半徑增加而變大，碳管長度差增加而減小。

Carbon nanotube is the newest material in twenty-one century and will be widely used in high tech products and civil things. As a result, understanding the mechanical properties of the single-walled carbon nanotube (SWNT) is very important in application of the carbon nanotube.So in this paper, we use molecular dynamics method to calculate the mechanical properties of the tube and select the Tersoff potential to represent the force between carbons. Then start the simulation of tension, compression and torsion of the tube with fixed number of carbons, volume and temperature. Using its relationship between energy and strain to calculate its Young’s modulus and Shear modulus. In this, there are two ways to compare its mechanical properties. One is to fix the radius of the tube and change its length. The other is fix the length of the tube and change its radius. Comparing the result,we find the Young’s modulus of SWNT is 0.613 Tpa and the shear modulus is 0.396 Tpa. And it seems that the Young’s modulus have no rule or trend. Shear modulus will be bigger with the increasing of radius and smaller with the decreasing of the length.