金属纳米团簇在石墨烯莫尔模板表面成核与生长机理研究

It is found in experiments that large area graphene monolayer with high quality can be grown on metal surfaces. Moiré patterns are formed between the grapheme and substrate. Such superstructures can act as ideal two dimensional templates for growth of metal nanocluster array. By this means, it is promising to make size-controlled nanostructured metal catalysts. This templated growth based on grapheme Moiré pattern has great potential for applications in metal and semiconductor nanodots, high-density storage materials and heterogeneous catalysis. However, there are still many important problems to be solved. It is still not clear about the selective nucleation mechanisms of the metal nanoclusters grown on the graphene Moiré template at preferential sites. The mechanism of the growth of metal nanoclusters deposited on graphene Moiré template is to be revealed. In this project, parameter sets for many-body potential functions between carbon and metal atoms will be constructed by fitting the binding energies to those obtained from first principles calculations. The diffusion barrier and adsorption energy of metal atoms on graphene Moiré strip will be calculated at different positions, and the diffusion behavior of metal atoms will be further analyzed at different regions of the graphene Moiré superstructure. The mechanism of nucleation of metal nanoclusters needs to be addressed. Using the fitted potential functions, we will find the graphene Moiré template that agrees well with the experiments by classical molecular dynamics simulations. In addition, dynamics simulations are performed for metal nanoclusters deposited on the graphene Moiré surface by molecular dynamics or Monte Carlo simulation, and to deduce the general laws of growth mechanism of graphene Moiré templates control the deposition of metal nanoclusters. These findings should provide a theoretical basis for large scale fabrication of regular arrays that are mono-dispersed uniformly sized, and highly ordered quantum dots of the metal nanocluster.

实验发现，金属表面可生长大面积高质量单层石墨烯，石墨烯形成周期性莫尔条纹，以其为模板能生长出大小和分布均匀的金属纳米点阵，有望制备尺寸可控的金属催化剂团簇，在金属和半导体量子点、高密度存储材料、异质催化等方面具有极大的应用潜力。但是其中有许多重要问题有待研究，金属纳米颗粒在石墨烯模板上成核位置的选择机制还有待揭示，金属纳米颗粒在莫尔模板上沉积生长的机理尚不清楚。本项目将采用第一性原理计算拟合出石墨烯与金属衬底相互作用的多体势参数，计算金属原子在石墨烯莫尔条纹表面上的吸附能和扩散势垒并分析其扩散行为，揭示金属纳米团簇的成核机理，应用拟合势参数采用分子动力学方法模拟出与实验结果一致的石墨烯莫尔模板，采用分子动力学和蒙特卡洛方法模拟金属纳米团簇在石墨烯莫尔模板表面的沉积过程，探索石墨烯莫尔模板对金属纳米团簇生长的调控规律，为制备出单分散、尺寸均一的大规模有序金属纳米团簇量子点阵提供理论指导。

实验发现，金属表面可生长高质量单层Graphene，Graphene形成周期性莫尔条纹，以其为模板能生长出大小和分布均匀的金属纳米点阵，有望制备尺寸可控的金属催化剂团簇，在金属和半导体量子点、高密度存储材料、异质催化等方面具有极大的应用前景。但碳基二维材料的热稳定性，纳米颗粒在二维材料基底上成核位置的选择机制及沉积生长的机理尚不明晰。本项目采用第一性原理计算及分子动力学方法研究碳基二维材料的热熔化性质，以便了解二维表面吸附特性；计算金属原子在Graphene表面上的吸附能和扩散势垒并分析其扩散行为，探究纳米团簇的成核机理；模拟金属纳米团簇在Graphene等模板表面的沉积过程，为制备出单分散、尺寸均一的大规模有序金属纳米团簇量子点阵提供理论指导。我们采用分子动力学方法研究了graphyne 和 graphdiyne的高温演化，表明单层的graphyne和graphdiyne在升温过程中会经历三个连续的相变。分别在2800和 2500 K时转变成无定形Graphene相，大约5000 K无定形Graphene熔化。基于密度泛函理论对Graphene吸附在Ni(111)、Ru(0001)等表面进行了研究，其稳定性以top-fcc结构最好，top-hcp结构次之。采用Morse和Lennard-Jones势模型对Graphene两个不等价C原子与Ni衬底间的相互作用进行拟合，给出了势参数。采用分子动力学模拟方法，对Graphene在Ni(111)、Ru(0001)表面吸附的动力学行为进行了模拟，当采用Morse描述C-Ni间的相互作用关系时，top-fcc、top-hcp结构的Graphene/Ni(111)体系的稳定性特征与实验结论吻合良好。为理解二维表面吸附特性，研究了一维锯齿型和扶手椅型的过渡金属纳米线在graphyne表面的电子和磁性质。基于第一性原理方法预测了两种新型二维多孔碳晶体，研究了氢化graphyne的动力学稳定性以及电子结构，还研究了Graphene带电量子点的量子阱。采用纳米压痕方法研究了Graphene和graphyne的杨氏模量，后者为前者的一半，约0.5Tpa。