密度泛函理论研究多巴胺在纯的,Fe和Ca掺杂的石墨烯材料表面的吸附机理

本论文用密度泛函理论方法研究了多巴胺在纯的,Fe和Ca掺杂的石墨烯上的吸附机理.通过它们之间的相互作用能,态密度,布局电荷,差分电荷密度分析发现多巴胺平行躺在纯的石墨烯表面主要是π…π,-CH…π相互作用,而垂直放在纯的石墨烯表面主要是-OH…π相互作用,这些都表现为典型的物理吸附.而Fe和Ca掺杂的石墨烯大大增强了多巴胺的吸附,主要体现为典型的化学吸附,因为掺杂金属原子与多巴胺的邻苯二酚羟基主要形成"bridge bidenate"or"monodenate"共价相互作用.而且我们发现"monodenate"共价作用不一定小于"bridge bidenate"共价作用,主要取决于相互作用原子之间最短距离的大小.研究结果有望为多巴胺-石墨烯基体系在生物组织工程,传感器方面的应用上提供有价值的理论指导.     

密度泛函理论研究草甘膦在纯的, 金属原子掺杂石墨烯表面的吸附机理

本研究采用密度泛函理论方法详细讨论了纯的石墨烯及Ti, Fe, Al, Ca原子掺杂石墨烯吸附草甘膦的机理.通过它们之间的吸附能,差分电荷密度,布居电荷,态密度分析发现草甘膦可以被纯的石墨烯及金属原子掺杂石墨烯不同程度地吸附.纯的石墨烯对草甘膦的吸附作用远不及掺杂石墨烯,其中,草甘膦在Ca掺杂石墨烯表面有最强相互作用.这是因为草甘膦与纯的石墨烯之间主要形成了-P=O…π,-COOH…π和-OH…π非共价的相互作用,而与掺杂石墨烯之间主要形成了Metal-O“单齿”和O-Metal-O“双齿”共价相互作用.本研究结果希冀为石墨烯在环境保护方面的应用提供有价值的理论指导.     

本征及掺杂石墨烯对2,3,7,8-四氯二苯并呋喃吸附机理的计算模拟研究

二噁英对人类和环境具有较高的毒性,因此,研制出有效的二噁英有机污染物的去除和检测方法尤为重要.本研究采用密度泛函理论模拟方法详细探讨了本征及Ti,Fe及Pt掺杂石墨烯对2,3,7,8-四氯二苯并呋喃(2,3,7,8-tetrachlorodibenzofuran,TCDF)二噁英污染物的吸附机理.研究结果表明,本征石墨烯及掺杂石墨烯表面对TCDF均有一定程度的吸附,而Ti和Fe掺杂石墨烯对TCDF的吸附远大于本征石墨烯对TCDF的吸附.主要原因是TCDF与本征石墨烯之间主要形成了π…π,C-H…π和C-Cl…π非共价的相互作用,而与掺杂石墨烯之间主要形成了metal-O共价相互作用.研究结果有望为石墨烯材料在二噁英污染物TCDF吸附方面的应用提供有价值的理论指导.     

石墨烯在Ni(111)表面生长机理的紧束缚计算研究

本文采用SCC-DFTB方法,研究了石墨烯在Ni金属(111)表面上的生长机理及在台阶面生长情况.结果分析表明,苯环在Ni表面吸附时以界面fcc构型总能最低,结构最为稳定.边缘生长时,附着在衬底表面上的石墨烯层中C原子活性从边缘向中间逐渐降低.在由(111)晶面和(111)晶面相交形成的台阶面上,石墨烯片层可连续生长,同时相对衬底表面发生一定偏转,在较大面积时将出现缺陷.改善石墨烯与衬底台阶处的界面不匹配情况将有利于其大面积高质量生长.     

石墨烯纳米带电子结构的紧束缚法研究

在推导出的一般复式格子的π电子紧束缚能量色散关系的基础上,通过假定石墨烯纳米带的电子横向限制势为无穷大硬壁势,导出石墨烯纳米带的能量色散关系及石墨烯纳米带或为金属或为半导体的条件.结果表明：石墨烯纳米带的电子结构与其几何构型（对称性及宽度）密切相关,所以通过控制几何构型,可将其调制成金属或不同带隙的半导体.这意味着石墨烯纳米带对于发展新型纳米器件具有重要意义. 关键词： 石墨烯纳米带 复式格子 紧束缚模型 电子结构     

石墨烯在Ni(111)表面生长机理的紧束缚计算研究

本文采用SCC-DFTB方法,研究了石墨烯在Ni金属(111)表面上的生长机理及在台阶面生长情况.结果分析表明,苯环在Ni表面吸附时以界面fcc构型总能最低,结构最为稳定.边缘生长时,附着在衬底表面上的石墨烯层中C原子活性从边缘向中间逐渐降低.在由(111)晶面和(1-11)晶面相交形成的台阶面上,石墨烯片层可连续生长,同时相对衬底表面发生一定偏转,在较大面积时将出现缺陷.改善石墨烯与衬底台阶处的界面不匹配情况将有利于其大面积高质量生长.     

密度泛函理论研究多巴胺在纯的, Fe和Ca掺杂石墨烯材料表面的吸附机理

本论文用密度泛函理论方法研究了多巴胺在纯的, Fe和Ca掺杂的石墨烯上的吸附机理. 通过它们之间的相互作用能, 态密度, 布局电荷, 差分电荷密度分析发现多巴胺平行躺在纯的石墨烯表面主要是π•••π, -CH•••π相互作用, 而垂直放在纯的石墨烯表面主要是-OH•••π相互作用, 这些都表现为典型的物理吸附. 而Fe和Ca掺杂的石墨烯大大增强了多巴胺的吸附, 主要体现为典型的化学吸附, 因为掺杂金属原子与多巴胺的邻苯二酚羟基主要形成“bridge bidenate” or “monodenate”共价相互作用. 而且我们发现“monodenate”共价作用不一定小于“bridge bidenate”共价作用, 主要取决于相互作用原子之间最短距离的大小. 研究结果有望为多巴胺-石墨烯基体系在生物组织工程, 传感器方面的应用上提供有价值的理论指导.     

基于气相沉积等离激元纳米粒子/三维石墨烯-镍泡沫复合结构的高灵敏度表面增强拉曼检测

本文提出一种基于气相沉积银纳米粒子和三维石墨烯-镍泡沫的复合等离激元结构.该结构是利用气相纳米团簇束流技术将高密度的银纳米粒子直接沉积于三维石墨烯-镍泡沫的表面制备而成.与传统银纳米结构相比,复合三维等离激元纳米结构具有"热点"数量多,局域场更强的特点,可作为基于表面增强拉曼技术的高灵敏度化学传感器.拉曼测试实验结果表明,该三维纳米结构在表面增强拉曼检测中可获得灵敏度高,重复性好的探针拉曼信号.通过进一步的理论模拟,发现该三维等离激元结构中增强的拉曼信号主要归因于纳米粒子与纳米粒子之间以及纳米粒子与石墨烯-镍泡沫衬底之间的多重近场耦合效应.     

介电层表面直接生长石墨烯的研究进展

作为21世纪备受瞩目的材料,石墨烯兼具优异的电、热、光与力学性质,具有十分广阔的研究价值与应用价值.目前主要通过在金属基底上生长获得石墨烯,并将其转移至目标介电层基底上以构筑电子器件.转移过程不可避免地引入了褶皱、裂纹、破损以及聚合物/金属残留,严重损害了石墨烯的性能.因而直接在介电基底上制备高质量的石墨烯薄膜具有重要意义.本文总结了近年来在介电衬底上直接生长石墨烯的研究进展:阐述了金属辅助法、等离子体增强法以及热力学或动力学调控法等多种生长手段;介绍了多种介电/绝缘基底包括SiO_2/Si,Al_2O_3,SrTiO_3,h-BN,SiC,Si_3N_4以及玻璃表面生长石墨烯的特点与性能,分析了其可能的生长机理.根据拉曼谱图、薄层电阻、透光率、载流子迁移率等评估指标,将多种方法得到的石墨烯质量进行了总结与比较,并提出了直接在介电衬底上生成石墨烯的研究难点与趋势.     

Y掺杂空位石墨烯对NO及CO气体表面吸附的第一性原理研究

摘　要：基于第一性原理的计算方法，建立了本征石墨烯、空位石墨烯及钇( Y)掺杂空位石墨烯模型，并计算了CO、NO在三类石墨烯表面的吸附过程. 从表面能、吸附结构、吸附能和态密度四个方面进行分析讨论，研究掺杂Y对CO、NO气体吸附性能的影响. 结果表明：CO、NO与本征石墨烯之间的吸附为弱的物理吸附，掺杂Y后增强了材料表面对CO、NO的吸附效果，最大吸附能分别为7.414eV、6.702eV，属于化学吸附；掺杂Y使空位石墨烯费米能级附近有了更多的活跃电子，其吸附NO后体系由半金属转变为金属特性，该特性能为开发更加优良的石墨烯气敏材料提供理论支持.     

Electronic structures and vibrational properties of coronene on Ru(0001): first-principles study

We calculate the configurations, electronic structures, vibrational properties at the coronene/Ru(0001) interface, and adsorption of a single Pt atom on coronene/Ru(0001) based on density functional theory calculations. The geometric structures and electronic structures of the coronene on Ru(0001) are compared with those of the graphene/Ru(0001). The results show that the coronene/Ru(0001) can be a simplified model system used to describe the interaction between graphene and ruthenium. Further calculations of the vibrational properties of coronene molecule adsorbed on Ru(0001) suggest that the phonon properties of differently corrugated regions of graphene on Ru(0001) are different. This model system is also used to investigate the selective adsorption of Pt atoms on graphene/Ru(0001). The configurations of Pt on coronene/Ru(0001) with the lowest binding energy give clues to explain the experimental observation that a Pt cluster selectively adsorbs on the second highest regions of graphene/Ru(0001). This work provides a simple model for understanding the adsorption properties and vibrational properties of graphene on Ru(0001) substrate.     

Cyanogen on Ni(110): an experimental and theoretical study

Adsorption of cyanogen, C₂N₂, on a Ni(110) surface has been investigated by combining low energy electron diffraction, thermal desorption and angular resolved ultra-violet photoemission experiments as well as model cluster calculations using the linear combination of Gaussian-type orbitals local density functional method as well as a force field approach. Results of mirror plane photoemission experiments on the ordered c(2 × 2) monolayer could be rationalized by invoking adsorbates bonded to the surface via the π electrons, with their axis oriented along the [001] direction, across the grooves of the (110) surface, leading to an assignment of all six adsorbate-derived valence orbitals. However, unlike in a previous study on the analogous chemisorption system Pd(110)/C₂N₂, only one mirror plane was detected. A possible tilt of the adsorbates in the (1 0) plane was related to crowding on the closer spaced nickel surface by estimating the lateral interaction within the adsorption layer using force field models. Electronic structure calculations on various chemisorption model clusters confirmed the experimental orbital assignment and the orientation of the adsorbate axis essentially along the [001] direction. Best agreement with UPS data was found for the orbital splitting pattern of an adsorption geometry where the C-N groups bind sideways on-top of nickel atoms in the first crystal plane. On the other hand, bonding along in the troughs of the (110) surface leads to a distinctly different ordering of the valence orbitals, at variance with the experimental assignment.     

Structures of Pt clusters on graphene by first-principles calculations

The interactions between Pt_n clusters (n?13) and a graphene sheet have been investigated by first-principles calculations based on density functional theory. For single Pt-atom and Pt₂-dimer adsorptions, the stable adsorption sites are bridge sites between neighboring carbon atoms. When the number of Pt atoms in a cluster increases, the Pt-C interaction energy per contacting Pt atom becomes smaller. For smaller clusters (3?n?7), the adsorption as a vertical planar cluster is more stable than that as parallel planar or three-dimensional (3D) clusters, due to the stability of a planar configuration itself and the stronger planar-edge/graphene interaction, while the adsorption as a parallel planer cluster becomes stable for larger cluster (n?7) via the deformation of the planar configuration so as to attain the planar-edge/graphene contact. For much larger clusters (n?10), the adsorption as a 3D cluster becomes the most stable due to the stability of the 3D configuration itself as well as substantial Pt-C interactions of edge or corner Pt atoms. The interfacial interaction between a Pt cluster and graphene seriously depends on the shape and size of a cluster and the manner of contact on a graphene sheet.     

Electronic structures and coronene on Ru（0001）： vibrational properties of first-principles study

We calculate the configurations,electronic structures,vibrational properties at the coronene/Ru(0001) interface,and adsorption of a single Pt atom on coronene/Ru(0001) based on density functional theory calculations.The geometric structures and electronic structures of the coronene on Ru(0001) are compared with those of the graphene/Ru(0001).The results show that the coronene/Ru(0001) can be a simplified model system used to describe the interaction between graphene and ruthenium.Further calculations of the vibrational properties of coronene molecule adsorbed on Ru(0001) suggest that the phonon properties of differently corrugated regions of graphene on Ru(0001) are different.This model system is also used to investigate the selective adsorption of Pt atoms on graphene/Ru(0001).The configurations of Pt on coronene/Ru(0001) with the lowest binding energy give clues to explain the experimental observation that a Pt cluster selectively adsorbs on the second highest regions of graphene/Ru(0001).This work provides a simple model for understanding the adsorption properties and vibrational properties of graphene on Ru(0001) substrate.     

Calculation of normal frequencies of adsorbed molecules by the LCGTO-MCP-LSD method

Density functional calculations have been performed to determine the equilibrium geometry and normal frequencies of the Pd₃(CCH₃) cluster (ethylidyne on Pd₃). We find promising agreement between the theoretically obtained frequencies and those of experimental studies for CCH₃ on the Pd(111) surface. The effect of the metal cluster relaxation on the calculated equilibrium geometry and normal frequencies is examined.     

密度泛函理论研究CO与Nin（n=1—6）团簇的相互作用

采用密度泛函理论对CO吸附在镍团簇表面进行了系统研究.结果表明,Ni_nCO团簇的最低能量结构是在Ni_n团簇最低能量结构的基础上吸附CO生长而成,CO的吸附没有改变Ni_n团簇的结构;CO分子在Ni_n团簇表面发生的是非解离性吸附,与优化的CO键长（0.1138?nm）相比,吸附后C—O键长变长（0.1180—0.1214?nm）,表明吸附后C—O键被削弱,CO分子被活化.自然键轨道分析表明,CO分子只与最近邻的Ni原子发生相互作用;CO分子与Ni原子相互作用的本质是CO分子内的杂化轨道与Ni原子3d, 4s, 4p轨道相互作用的结果. 关键词： nCO团簇')" href="#">Ni_nCO团簇 n团簇')" href="#">Ni_n团簇 平衡结构 电子性质     

金属纳米薄膜在石墨基底表面的动力学演化

采用分子动力学方法研究了金属Au和Pt纳米薄膜在石墨(烯)基底表面的动力学演化过程,探讨了金属薄膜和石墨(烯)基底间的相互作用对金属纳米薄膜在固态基底表面的去湿以及脱附的动力学演化的影响.研究结果表明,在高温下,相同层数的Au和Pt纳米薄膜在单层石墨基底表面上存在不同的去湿现象,主要表现为厚度较小的Pt纳米薄膜在去湿过程中有纳米空洞形成,而同样厚度的Au薄膜在去湿过程中没有形成空洞.Au和Pt两种金属薄膜在高温下都去湿形成纳米液滴,这些液滴最终都以一定的速度脱离基底.在模拟的薄膜厚度范围内(0.2—2.3 nm),Au和Pt纳米液滴脱离基底的速度随厚度增加表现出不同的变化规律.Pt纳米液滴的脱离速度随薄膜初始厚度的增加先增加后减少,而Au脱离速度随厚度的增加先减少,达到一个临界厚度后脱离速度突然迅速增加.利用薄膜与基底间相互作用的不同导致去湿过程中的黏滞耗散不同,定性分析了这种变化规律的原因.此外,进一步研究还发现金属液滴的脱离时间与薄膜厚度和模拟温度的依赖关系,发现脱离时间随薄膜厚度的增加而增加,随模拟温度的升高而减小.这些研究结果可以为金属镀膜、浮选、表面清洁、器件表面去湿等工业生产过程提供理论指导.     

合金效应加强水分子在PtRun团簇上的吸附作用

利用第一性原理计算方法,研究合金效应对PtRu_n-1（n=2-14）和H₂O-PtRu_n-1（n=2-14）体系的几何构型、稳定性及吸附水特性的影响.结果表明：铂原子替代钌原子的能量较低,容易与钌团簇形成合金,铂原子喜欢占据配位数较低位置.相对于纯钌团簇,合金效应很大程度上提高了水分子在PtRu_n团簇上的吸附能.考虑范德瓦尔斯力后,水分子在PtRu₇上的吸附能增大,分解势垒降低,水分子可以在PtRu₇上分解.铂钌合金更适合做分解水制取氢气的催化剂.     

First-principle study of magnetism induced by vacancies in graphene

Spin-polarized density functional theory has been used to study the effects of vacancy defects on the magnetic properties of graphene. Structural optimization shows that introducing a carbon vacancy cluster into a graphene sheet changes the spatial distribution of the neighbor atoms, particularly those located around the vacancy. From spin-polarized DOS and LPDOS calculations, we find that only vacancies containing unpaired electrons show magnetism. These results lead us to formulate a relation between the vacancy-induced magnetic moment and the size and shape of the vacancy clusters in graphene sheet.     

Role of Van der Waals Forces in Graphene Adsorption over Pd, Pt, and Ni

We report ab initio computations with the Vienna Ab initio Simulation Package (VASP) aimed at elucidating the adsorption mechanism of graphene-like structures on (111) Pd, Pt, and Ni surfaces. To study the adsorption properties, we simulate an already-formed graphene layer. We present a comparative discussion of the graphene interactions with the three metals, focusing on the very particular adsorption of graphene over Pd.