奈米管之點缺陷計算：第一原理計算

Defects in nanotubes：ab-initio study

林佶鋒(Chi-Feng Lin)

指導教授 ： 薛宏中

淡江大學/理學院/物理學系碩士班/碩士(2006年)

https://doi.org/10.6846/TKU.2006.00145

摘要

由於近代的固態能帶理論發展的相當成功，配合高速的電腦運算功能，已被證實為研究材料微觀性質之利器。舉例而言，在過去的計算材料研究中，針對了單層石墨平面以及碳奈米管，在各項點缺陷的實驗中，發現非常特殊之磁性變化。在本文中，我們採用了氮化硼分子結構，來取代平面和奈米管結構中的碳原子；透過DFT理論以及GGA近似方法的計算，觀察在基態中，空洞點缺陷以及原子取代點缺陷，造成原子位置以及能帶結構的影響與改變，並計算結構形變過程中，產生磁矩之大小。另一方面，我們改變奈米管的長度，模擬軸向拉力造成形變後，研究氮化硼奈米管的磁矩變化。我們發現：點缺陷對於這些奈米結構，所產生之磁性效應，具有相當的一致性。

關鍵字

點缺陷 ； 奈米管 ； 氮化硼 ； 第一原理

並列摘要

The combination of the well-established solid-state theory and high performance computational facility provides a promising methodology to elucidate the microscopic properties of versatile materials. For instance, the previous calculations indicated that point defects gave rise to unique magnetic properties in both graphene and carbon nanotubes. In this thesis, we investigate the defect effects on III-V semiconductor, boron-nitride, in the corresponding nano-structures. Defect-induced atomic geometrical distortion, electric band-structure modification, and magnetic moment around the defect center are calculated by means of a Density Functional Theory (DFT) scheme in which a generalized gradient approximation (GGA)is adopted to approximate the exchange-correlation potential. On the other hand, we also perform calculations with respect to various lengths of the BN nanotubes to study the uni-axial stress effects on the defect-induced magnetization.

並列關鍵字

Defect ； nanotubes ； ab-initio

參考文獻

[2] S. Iijima, “Helical microtubules of graphitic carbon”, Nature 354, 56 (1991).

[3] M. C. Payne, M. P. Teter, D. C. Allan, T. A. Arias, J. D. Joannopoulos, “Iterative minimization techniques for ab initio total-energy calculations：molecular dynamics and conjugate gradients”, Review of Modren Physics 64, 1045 (1992)

”, Nature 418, 716 (2001).

[6] Yong-Hyun Kim, Jin Choi, and K. J. Chang, “Defective fullerenes and nanotubes as molecular magnets: An ab initio study”, Phys. Rev.B 68, 125420 (2003)

[7] Jin Choi, Yong-Hyun Kim, K. J. Chang, and David Toma´nek, “Itinerant ferromagnetism in heterostructured C/BN nanotubes”, Phys. Rev.B 67, 125421 (2003)