小型鈹鋰合金原子團吸附在矽表面之密度泛函數計算

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Title:	小型鈹鋰合金原子團吸附在矽表面之密度泛函數計算 Density Functional Theory Calculations for the Small Beryllium-Lithium Alloy Clusters Adsorption on Silicon Surfaces
Authors:	蔡臣軒
Contributors:	應用化學研究所
Keywords:	密度泛函理論基底函數矽氫原子團簇鈹鋰合金原子團單位晶格
Date:	2007
Issue Date:	2010-07-05 09:27:36 (UTC+8)
Abstract:	本研究是利用LixBey (x≦2, y≦2) cluster吸附在代表理想Si(111)表面 (即剛切割還未重建之表面)的SimHn clusters上。使用GAUSSIAN 03程式組中含電子相關之B3LYP方法基底函數並配合6-31G基底函數(basis set function)進行一系列密度泛函理論法(Density Functional Theory)的計算。首先針對同樣的LixBey進行不同面向在不同表面位置進行吸附幾何結構最佳化，再以此為基礎，藉由計算出來的結果來探討其結構的變化、鍵長和鍵角的改變，並比較各種區域穩定結構能量的高低。本研究中我們先從小的基底(2 unit cells)的矽氫原子團簇(SimHn clusters)開始探討，再增加至四個unit cells。這樣做的原因在於經由吸附後的結果發現矽氫原子團簇在較小時，其週邊的矽原子由於較自由的關係，造成結構有相當程度的扭曲。但是當矽氫原子團簇加大後，扭曲的情形改善許多，代表吸附後的結構趨於穩定，但計算時間也大量增加。研究結果顯示，2Li+Be (兩個獨立Li原子與一個Be原子)和2Be+Li (兩個獨立Be原子與一個Li原子)吸附後較吸附前Li-Be之間距離呈現縮短情形，其値接近自由的Li-Be分子之鍵長(~2.60 Å)或較為縮短，這樣的結果顯示Li-Be這兩個金屬原子之間鍵結作用力增強，會鍵結形成LiBe分子，這點可從原子軌域方面進ㄧ步做解釋。 We investigated bonding and optimized geometries of 2Li+Be、2Be+Li adsorbed on the Si(111) surfaces at the B3LYP/6-31G level. In the case of Si(100), the Si9H12 cluster was used to represent the surface unit with one Si=Si surface dimmer, while in the case of Si(111),different sizes of Si-H clusters were used, depending on the extent of marginal distortion of the unit cell. General speaking, the bond lengths in 2Li+Be and 2Be+Li adsorbates are greatly reduced due to the flowing of charge density from metal antibonding orbitals into the surface dangling bonds.
Appears in Collections:	[Department of Chemistry & Graduate Institute of Applied Chemistry ] thesis

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