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物理学院“博约学术沙龙”系列报告 (总第 128 期)

发布日期:2016年11月23日
时间:2016年11月23日(星期三)下午3:00
地点:中心教学楼610
 
报告一:硕士生报告    时间:15:10-15:40
题  目:The Kinetics of Spherical Interface in Crystal Growth
报告人:付美芹           指导老师:吕勇军
摘要:The crystal growth of Cu, Al, NiAl and CuZr in the inception after homogeneous nucleation is studied by using molecular dynamics simulations. The growth rates of spherical crystals are found to increase with increasing grain radius. To clarify the mechanism of the accelerated growth, the solid-liquid interface energies are calculated. The results do not show the radius dependence, andtherefore the capillarity effect does not contribute to the enhancement of the growth rate. It is found that the interface kinetics dominates the growth process. The simulations show that the interface thickness and the Jackson a-factor increase in a similar way as the growth proceeds, indicating that the interface becomes increasingly rough during growth. Due to the interface roughening, the fraction of repeatable growth sites at interface, f, which is proportional to the growth rate based on the collision- and the diffusion-limited growth model, is proposed to actually increase in growth. An attachment rate, which is defined as the fraction of atoms that join the crystal interface without leaving, is used to approximate f, displaying a linear increase. With this approximation, we predict the growth rates as a function of crystal radius, and the results qualitatively agree with those from the direct simulations. This work gives an insight into the crystal growth in the initial period after homogeneous nucleation and leads to a further understanding of interface kinetics during metal crystallization.
 
报告二:硕士生报告    时间:15:40-16:10
题  目:载体调控对Au团簇的结构和性能的影响
报告人:高锦花        指导老师:江兆潭
摘要:近年来, 金纳米团簇(Aun)由于其特殊的物理化学性质得到了人们的广泛关注。本文采用密度泛函理论方法对Aun团簇分别吸附于MgO(001)和TiO2(101)表面的结构和性质进行了模拟计算、分析和比较。结果表明,Aun吸附于氧化物表面时其催化活性增加,且由于团簇与基底表面的电荷转移,吸附于MgO(001)表面时,Aun带负电,而吸附于TiO2(101)表面时,Aun带正电,这种表面电荷的变化使得Au纳米团簇可对不同体系具有催化活性。另外,负载于氧化物表面时Aun的p、d态密度均会发生明显的变化,这说明基底表面的电子对Au团簇的电子态结构产生了影响,从而对Aun的结构和电子性能等产生了显著的影响。该研究结果可为Aun作为光催化剂在氧化还原反应中的选择性研究提供理论参考和数据支持。
 
报告三:硕士生报告    时间:16:10-16:40
题  目:The preparation and Optical properties research of Single-layer MoS2 and CdS-MoS2 micro-nano structure
报告人:徐乾坤           指导老师: 邹炳锁
摘要:
二硫化钼晶体为六方晶系,带隙为1.29eV的间接带隙半导体。单层二硫化钼就有类石墨烯结构,成为带隙为1.90eV直接带隙半导体。类石墨烯二硫化钼以其二维层状夹心结构和特殊的能带结构,在光电器件领域具有很大的应用前景。通过化学合成的方法制备单层二硫化钼及其与硫化镉的微纳复合结构,通过微区光谱手段研究这些单层或者微纳结构中激子复合和驰豫性质,深入了解其电子结构各种光学性质,为下一步光电器件应用开辟道路。
Molybdenum disulfide crystal belongs to the hexagonal system and it`s the indirect band gap semiconductor whose band gas is 1.29eV. Single-layer molybdenum disulfide has the graphene structure, and becomes the direct band semiconductors of 1.90 eV band-gap. Graphene-like molybdenum disulfide would have great application prospect as for its two-dimensional laminar layer structure and special band structure. We use the chemical vapor deposition method to synthesis single-layer molybdenum disulfide and the micro-nano composite structure with cadmium sulfide. Then we research the exciton recombination and relaxation effect by the micro zone spectrum method. Deep understanding of the optical properties is made for the electronic structure of molybdenum disulfide, which would create  smooth way for the next photoelectric device application.
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