氫能已逐漸成為未來的重要能源，然而由於氫的密度很小，再加上安全的考量，故氫的儲存一直是個重要的課題。除了傳統的方法之外，儲氫合金與奈米碳材被視為是有潛力的氫能材料，其中尤以奈米碳管最受到矚目。
本論文將採用以密度泛函理論為基礎的第一原理計算軟體-VASP（Vienna Ab-initio Simulation Package），主要是採用以廣義梯度近似法（Generalized gradient approximation）發展而來的PW91勢能來描述交換相關能。內容主要是針對（3,3）型的奈米碳管，尋找其最佳吸附狀態，並分析其電荷轉移，探討儲氫機制。在物理吸附方面，分別比較不同型態的氫分子在接近（3,3）型與（4,2）型碳管時，其所對應的束縛能與吸附位置，並討論其中的差異，發現當碳管半徑約為2時，束縛能約為-0.07eV，與半徑為3.39的（5,0）碳管相比，顯示吸附位置與束縛能跟半徑有關；在化學吸附方面，亦先求出吸附位置，並利用碳原子與氫原子的電荷密度分佈，證實了化學吸附時的解離現象。

Hydrogen energy is believed to be one of the best substitutes for fossil fuels in the future. However, due to its small density and safety consideration, its storage has been an important issue. In addition to the traditional methods, hydrogen storage alloy and carbon nano-materials are regarded as a potential hydrogen-storage materials, especially carbon nanotubes.
The objective of this thesis is to study the hydrogen molecule adsorption upon the (3,3) carbon nanotube by the first principle calculation software, VASP, which is based on the density functional theory. The exchange-correlation energy is calculated using the generalized gradient approximation (GGA). Moreover, the PW91 parameterization is adopted. The most stable adsorption state and the charge transfer are investigated to understand the detailed mechanism of the process. For the physical adsorption, we compare the binding energy and adsorption position, when different types of hydrogen molecule are approaching the carbon nanotubes. For the chemical adsorption, we obtain the adsorption position first, and then confirm the dissociation by using the charge density distribution between the carbon atom and hydrogen atom. Finally, the phenomena and detailed mechanism of these adsorption are evaluated and discussed. It is found that when the radius of the tube is around 2, its binding energy of physisorption is about -0.07eV.

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