有缺陷之三角形類石墨烯硼氮奈米結構之密度泛函數計算研究

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Title:	有缺陷之三角形類石墨烯硼氮奈米結構之密度泛函數計算研究 A Density Functional Study on the Defective Triangular Graphene-like BN Nanostructures
Authors:	邱珮盈
Contributors:	化學系應用化學碩士班
Keywords:	石墨烯三角形奈米片硼氮三角形奈米片 Graphene Triangular nanoflakes BN-TNFs
Date:	2015
Issue Date:	2016-02-24 14:25:05 (UTC+8)
Abstract:	石墨烯硼氮類似物稱為白石墨烯，本論文乃以密度泛函中的B3LYP法研究含缺陷之以硼為邊氮為頂的白石墨烯三角形奈米薄片(BN-TNFn)，其中n = 4~6為每邊六角環數目。由於薄片尚不夠大，在中央地區挖掉一個B或N原子後，結構重建的結果會因邊緣效應普遍呈現非平面。當半徑相近的C或O原子吸附在重建的破洞上方後，平面結構仍難回復，但C較具有縫補破洞的效果，O反而造成更大破洞或結構扭曲，這是因為C可與四個原子鍵結，O只能與兩個原子鍵結的緣故。如果直接將中心B或N換成雜質C或O情形也類似，只是C取代時平面變形較不嚴重；若換成O，反而從沒有破洞變成有破洞，而且造成去平面化。從平均結合能來看，破洞被吸附之後的產物比直接取代的產物還穩定。然而，不管是單單只有破洞、有雜質吸附在破洞、或直接取代，BN-TNFn的磁性都大大降低。 The boron nitride counterpart of graphene is the white graphene. In this thesis we employed the B3LYP method to investigate the B-edged (with N vertices) triangular nanoflakes of white graphene (BN-TNFn), where n = 4~6, being the number of hexagonal ring along each side. Because the area of BN-TNF4~6 are not wide enough, geometric reconstructions rendered non-planar species due to the edge effect after a vacancy was made by removing a central B or N atom. When an adatom C or O, which has similar sizes with B and N, was adsorbed by the reconstructed vacancy, the original flatness still could not be restored. However, C would stitch the hole, making it smaller, while O made the hole even larger and structure more distorted. This is because the bonding capacity of C and O are 4 and 2, respectively. Direct substitutions (doping) of a central B or N by C or O gave similar results. C-doping caused less structural distortion; however, O-doping opened a vacancy, making obvious structural changes. According to the mean binding energy, products from adatom adsorption were more stable than those from direct doping. Magnetism were greatly quenched by a vacancy, an adatom, and a dopant as compared to the pristine BN-TNF4~6.
Appears in Collections:	[Department of Chemistry & Graduate Institute of Applied Chemistry ] thesis

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