锗烯与碱金属原子构成杂化相的密度泛函研究

发布时间：2018-04-19 06:32

本文选题：锗烯 + 饱和吸附　；参考：《湘潭大学》2017年硕士论文

【摘要】：锗烯和硅烯均是新型类石墨烯二维蜂窝状结构晶体材料,二者是具有褶皱结构的二维单原子层薄膜,但是不同的是锗烯的翘曲高度0.737?大于硅烯0.44?。基于这个原因,锗烯具有比硅烯更强的自旋轨道耦合效应。目前,研究人员已经成功在金属Pt(111)面和Au(111)表面制备出单层锗烯。为了更好的利用锗烯的电子性质,各种调节方法得到了很大的关注。本论文采用基于密度泛函的第一性原理计算方法,开展了锗烯与碱金属原子构成新型杂化相的结构和电子性质研究。获得的主要结论有:1、考虑自旋轨道耦合效应,通过对锗烯饱和吸附形成的碱金属元素复合新相Ge2X2(X=Li、Na、K、Rb)进行分析,探索了形成的新相的稳定性。通过对形成能的计算,发现它们均可能在室温下形成稳定的杂化结构。Li、Na、K原子与锗烯形成的新相的形成能比纯锗烯更低,预示了复合新相比单层锗烯具有更高的稳定性。通过比较Ge2Li2复合新相与锗烯饱和氢化结构的形成能,发现Ge2Li2复合新相的稳定性甚至比锗烯饱和氢化形成的复合物稳定性更高。随着最近锗烯饱和氢化物的实验制备成功,我们的计算预示了锗烯饱和锂化新相制备的可能性。通过Bader电荷分析,揭示了锗和碱金属原子之间主要通过离子键结合,但仍存在部分共价成分。能带计算发现,饱和锂化锗烯新相是直接带隙半导体,具有0.14eV的能隙。其它碱金属原子与锗烯构成的新相均呈现金属性质。2、考虑自旋极化效应计算,对锗烯半饱和吸附碱金属原子形成的Ge2X1(X=Li、Na、K、Rb)新相结构进行了稳定性、电子和磁性质研究。通过稳定性、电荷转移、成键方式进行对比,发现锗烯半饱和吸附碱金属与锗烯饱和吸附碱金属的性质规律基本一致。但Li、Na、K原子与锗烯形成的稳定的半饱和吸附结构均呈现金属性,且在费米面及导带中显示出弱的极化性质。计算发现,半饱和锂化锗结构在与Li相邻的Ge原子上具有0.48μB的局域磁矩,预示了采用该种半饱和吸附锂结构可作为自旋器件材料开展应用。
[Abstract]:Germane and silicene are new graphene like two dimensional honeycomb structure crystal materials, they are two dimensional single atomic layer thin films with fold structure, but the warpage height of germane is 0.737?It is larger than silicene 0.44.For this reason, germane has a stronger spin-orbit coupling effect than silicene.So far, the researchers have successfully prepared monolayers germanium on the surface of metal Ptn111 and Aut111).In order to make better use of the electronic properties of germanium, various regulation methods have been paid much attention.In this paper, the structure and electronic properties of a new hybrid phase composed of germane and alkali metal atoms are studied by using the first principle method based on density functional.The main conclusions obtained are: 1, considering the spin-orbit coupling effect, the stability of the new phase formed by saturated adsorption of germanium (GE _ 2X _ 2X _ (2) O _ (X _ (2)) X _ (Li) Na _ (+) K _ ((+)) Rb) was investigated by means of the analysis of the new phase formed by GE _ (2) X _ (2).Through the calculation of the formation energy, it is found that they can form stable hybrid structure at room temperature. The formation energy of the new phase formed by the atoms of Li-NaK and germanium is lower than that of pure germane, which indicates that the composite new germanium has higher stability than the monolayer germanium.By comparing the formation energy of the new phase of Ge2Li2 and the saturated hydrogenation structure of germanium, it is found that the stability of the new phase of Ge2Li2 is even higher than that of the complex formed by saturated hydrogenation of germanium.With the recent successful preparation of germane saturated hydride, our calculation indicates the possibility of the preparation of new phase of saturated lithiation of germane.By Bader charge analysis, it is revealed that the bonding between GE and alkali metal atoms is mainly by ion bond, but some covalent components still exist.The energy band calculations show that the saturated lithium-germanium new phase is a direct-band gap semiconductor with the band gap of 0.14eV.The new phases of other alkali metal atoms and germane show metal properties. Considering the spin polarization effect calculation, the stability, electronic and magnetic properties of the new phase structure of GE _ 2X _ (1) X _ (+) K _ (K _ (B) Rb) formed by the semi-saturated adsorption of GE _ (2) X _ (1) O ~ (2 +) on alkaline metal atoms have been studied.By comparing the stability, charge transfer and bonding methods, it is found that the properties of the semi-saturated adsorbed alkali metals of germane are basically consistent with those of germane saturated adsorbed alkali metals.However, the stable semi-saturated adsorption structures formed by Li-Na ~ (2 +) K atoms and germanium show gold properties, and show weak polarization in Fermi surface and conduction band.It is found that the semi-saturated GE structure has a local magnetic moment of 0.48 渭 B on the GE atom adjacent to Li, which indicates that the semi-saturated adsorbed lithium structure can be used as a spin device material.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.1

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