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    Please use this identifier to cite or link to this item: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/32679


    Title: 矽量子點物理特性之理論計算
    Other Titles: Theoretical investigation of the characterization of silicon quantum dots
    Authors: 董育材;Dung, Yu-tsai
    Contributors: 淡江大學化學學系碩士班
    王伯昌;Wang, Bo-cheng
    Keywords: 矽量子點;能隙;silicon quantum dots;computational chemistry;energy gap;SIESTA;VASP
    Date: 2006
    Issue Date: 2010-01-11 02:32:49 (UTC+8)
    Abstract: 使用半經驗AM1、PM3及全始算密度泛函理論等計算方法,探討具有Td及Ih結構的矽量子點之電子結構,在密度泛函理論計算使用的基底函數包括了6-31G*與LANL2DZ,另外還使用了SIESTA軟體的局域密度近似(LDA)方法及VASP軟體探討矽量子點的電子結構。在我們的研究中,Td結構的矽量子點可以計算到Si281H172,而Ih結構僅有Si20H20、Si100H60及Si280H120這三種。從我們計算得到的能隙值看到,矽量子點的能隙會隨著其直徑的變大而減少;以密度泛函理論B3LYP//SIESTA方法所計算得到矽塊材的能隙會比較接近實驗值,而LDA方法計算的結果會低於實驗值,AM1//SIESTA及PM3//SIESTA的結果會高於實驗值。在不同取代基的影響下,Si35(CH3)36會略低於Si35H36的能隙值,而Si35(OH)36則是低於Si35H36的能隙值,這可能因為接有推電子基團會使得矽量子點的能隙下降。
    The optimized geometries and the electronic structures of hydrogenated silicon clusters which include the Td and Ih symmetries, were generated by using the semi-empirical AM1, and PM3 methods, the density functional theory (DFT) B3LYP method with the 6-31G* and the LANL2DZ basis sets as well as the local density functional approximation (LDA) implemented in SIESTA package. The Td symmetry hydrogenated silicon clusters with Si5H12 up to Si281H172 were used in this study. For the Ih symmetry, we calculated Si20H20, Si100H60 and Si280H120 clusters only. Theoretically, the energy gap between HOMO and LUMO is size dependent. The calculated energy gap is decreased while the diameter of silicon cluster is increased. Compared different calculated results, we conclude that the calculated energy gap by DFT B3LYP//SIESTA is closed to that of experimental data. LDA/SIESTA result is underestimate to the experiments. Contrarily, the AM1//SIESTA and PM3//SIESTA results are overestimate to the experiments. For the investigation of substituent effect, the calculated energy gap of Si35H36 is closed to that of Si35(CH3)36 and is higher than that of Si35(OH)36. Concludly, the electron-withdrawing group may increase the energy gap of silicon cluster.
    Appears in Collections:[化學學系暨研究所] 學位論文

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