钾纳米团簇和表面的局域应变及3p轨道能量钉扎

发布时间：2018-02-08 17:23

本文关键词： K纳米团簇 K(110)表面 BOLS 能量钉扎芯能级偏移　出处：《湘潭大学》2015年硕士论文　论文类型：学位论文

【摘要】：在块体材料表面和纳米材料的一系列研究中,人们致力于开拓并透彻了解这两者所具有的新颖的物理特性。在研究与低维材料系统有关的现象时,因为连续介质力学和近代量子理论等经典理论方法都遇到了一些难以突破的瓶颈,致使相关的实验测量优先于理论研究,且很少将低维材料与材料表面用低配原子这一概念联系在一起。通过构筑低配位原子间相互作用关系的理论模型,我们揭示了低维材料和块体材料表面部分不同于孤立原子和理想块体材料内部原子的相关物理机制。通过结合键序-键长-键强理论、紧束缚近似方法、密度泛函理论计算、X-射线光电子能谱测量、以及区域选择光电子谱,我们获得了与原子配位数相关的K(110)表面和K纳米团簇的局域晶格应变、3p芯能级偏移等定量信息,总结如下:1.经计算得到,K孤立原子相应的3p轨道芯能级为15.595±0.003 eV,标准差为0.003,K块体对应的3p轨道芯能级为18.353 eV,因此可知,钾块体相对于孤立原子能级的能级偏移量为2.758 eV。2.我们认为,孤立原子和理想块体内部的有效原子配位数分别为0和12,而我们测量的K(110)表面第二层和第一层的有效原子配位数分别为5.81和3.93,且表面最外层所产生的晶格应变、结合能相对密度变化、以及原子内聚能相对变化分别为2.76%、72.67%、和-62.46%。3.通过以上数据我们可以知道,K纳米团簇尺寸的减小会引起原子有效配位数的减少,并且进一步增加了表面原子的相对数目,增大了表面电子的贡献。结果表明:K(110)表面和K纳米团簇3p轨道芯能级的偏移来源于原子低配位引发的电荷致密化和量子钉扎对哈密顿量的微扰。理论与实验的一致性表明了体材料表面和原子团簇中低配位原子的键变短变强,相应原子的芯能级随着配位数的变化会发生有规律的改变。通过实验结果和计算以及理论预测得到局域晶格应变、能量密度、原子内聚能、以及它们低配关联的偏移量等定量信息,对满足特定结构和物理性能要求的纳米晶体的设计是非常有帮助的。
[Abstract]:In a series of studies on the surface of bulk materials and nanomaterials, efforts have been made to develop and understand thoroughly the novel physical properties of these two materials. Because the classical theoretical methods such as continuum mechanics and modern quantum theory have encountered some bottlenecks which are difficult to break through, the relative experimental measurement has priority over the theoretical research. The concept of low ligand atom is rarely associated with the low dimensional material and material surface. By constructing a theoretical model of the interaction between low coordination atoms, We reveal the physical mechanisms of the surface parts of low dimensional materials and bulk materials which are different from those of isolated atoms and internal atoms of ideal bulk materials. By combining the theory of bond order, bond length and bond strength, the tight-binding approximation method is proposed. The density functional theory (DFT) is used to calculate the X-ray photoelectron spectroscopy (XPS) measurements and the region-selective photoelectron spectra. We obtain the quantitative information such as the local lattice strain and 3p core energy level migration on the surface of K ~ (10) and K nanoclusters, which are related to the atomic coordination number. The results are as follows: 1.The corresponding 3p orbital core energy level of K solitary atom is 15.595 卤0.003 EV, and the standard deviation of 3p orbital core energy level corresponding to 0.003 K block is 18.353 EV. Therefore, the energy level deviation of potassium block relative to the isolated atomic level is 2.758 eV.2. we think, The effective atomic coordination numbers of isolated atoms and ideal blocks are 0 and 12, respectively, while the effective atomic coordination numbers of the second layer and the first layer are 5.81 and 3.93, respectively, and the lattice strain produced by the outermost layer of the surface is obtained. The relative density of binding energy and the relative change of cohesive energy in atoms are 2.76 ~ 72.67 and -62.46.3. from the above data, we can see that the reduction of the size of K nanoclusters will lead to the reduction of the effective coordination number of atoms. And further increase the relative number of atoms on the surface, The results show that the shift of the energy levels of the 3p orbital core on the surface and K nanoclusters originates from the charge densification induced by the low coordination of atoms and the perturbation of Hamiltonian by quantum pinning. The results show that the bond between the low coordination atoms on the surface of the bulk materials and the atomic clusters becomes shorter and stronger. The core energy levels of the corresponding atoms change regularly with the change of the coordination number. The local lattice strain, energy density and atomic cohesive energy are obtained by experimental results and calculations, as well as theoretical prediction. The quantitative information such as their low correlation offset is very helpful for the design of nanocrystalline which can meet the requirements of specific structure and physical properties.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O614.113;TB383.1

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