O2／Si（100）非重构表面LEPS相互作用势模型

对双原子分子Ｏ２与非重构Ｓｉ（１００）表面相互作用的ＬＥＰＳ半经验势模型进行了研究，其中表面作为具有波纹度的刚性表面进行处理。确立了系统的势能超曲面，得到的表面吸附特性Ｐ、Ｖ、Ｓｍｉｔｈ等人基于ＡＳＥＤ－ＭＯ方法的研究结果进行了定量对比分析。对不同入射条件下的分子－表面相互作用势也进行了研究。     

O2／Si（100）非重构表面相互作用过程的准经典轨迹研究

采用准经典轨迹计算方法对双原子分子Ｏ２与非重构Ｓｉ（１００）理想表面的散射过程进行了动力学研究。计算结果解释了氧分子与半导体表面相互作用中的能量传递机理，验证了前面工作所得到的ＬＥＰＳ半经验模型势的合理性。     

N_2/Fe(100)系统的半经验模型势

本文对双原子分子N_2和刚性、有波纹度的Fe(100)表面的相互作用势进行了研究。我们在已有的四体LEPS势模型的基础上,研究了LEPS势性质;得出了和已有实验数据相吻合的势参数,并且研究了N_2分子以不同方式入射到Fe(100)表面时分子一表面相互作用势U_(M-S)。     

O_2/Si(100)非重构表面相互作用过程的准经典轨迹研究

采用准经典轨迹计算方法对双原子分子O2与非重构Si（100）理想表面的散射过程进行了动力学研究。计算结果解释了氧分子与半导体表面相互作用中的能量传递机理，验证了前面工作所得到的LEPS半经验模型势的合理性。     

O_2/Si(100)-2×1重构表面相互作用过程的动力学研究

对双原子分子O2与Si（100）－2×1重构表面的相互作用过程进行了动力学研究。建立了相互作用系统的LEPS势能超曲面，并在此基础上采用准经典轨迹方法计算了不同特征吸附位上的分子运动轨迹，得到了与理想表面模型相比更为合理的表面吸附特性。     

中低能电子被分子散射总截面的计算

用光学势描述电子与构成分子的各原子的相互作用，根据可加性规划，对入射能量为１０－９００ｅＶ的电子被多原子分子Ｃ２Ｈ２散射的总截面进行了计算，并将结果与实验及其它理论计算结果进行了比较。     

双原子分子与表面的LEPS作用势的研究

本文对双原子分子与固体表面相互作用势的LEPS模型进行了研究。其中表面作为具有波纹度的刚性表面进行处理,并假定孤立的原子-原子、原子-表面作用势可用Morse势代表。基于N_2-W(110)系统,建立了势能超曲面,详细考察了势模型中可调参数的作用。在此基础上,计算了分子以不同方式接近表面时相互作用势的变化情况,以及作用势与分子核间距、取向、距表面高度等因素的关系,从而得出了对双原子分子-表面相互作用势具有普遍性的结论。     

H2分子在Ni（100）,（110）,（111）单晶表面吸附研究

本文采用改进模型势方法，计算了Ｈ２分子在Ｎｉ（１００）、（１１０）、（１１１）单晶表面解离吸附的反应途径与位能面。通过对比研究，讨论了氢分子在镍三种单晶表面解离吸附的反应途径和位能面的一般规律与趋势。     

N_2/Fe(100)相互作用的动力学研究

用准经典轨迹法对N2－Fe（100）系统进行了研究，分析了氮分子在Fe（100）面上的直接散射和离解性吸附等过程中的能量传递和重新分配，阐明了表面催化的机理。作为准经典轨迹法更为深入的应用，研究了主要LEPS势参数和势特性对初始离解吸附几率（S0）的影响，得出了S0随势特性变化的规律。     

芳烃体系分子导线的理论研究

在第一性原理的基础上,对芳烃体系与金表面形成的分子线的电学特性进行了理论研究,利用密度泛函理论计算了分子及扩展分子的电子结构;定量计算了分子与金表面的相互作用能和电子跃迁谱;利用弹性散射格林函数法研究了分子线的伏-安特性.计算结果表明:HOMO和LUMO间的禁带宽度、π电子数目、分子与金表面的相互作用以及分子轨道的扩展性等因素都将影响电子在分子线内的输运特性.     

分子离子在金属表面层区域飞行时产生的感应电势

本文采用“镜反射”模型研究了快速运动的双原子分子离子在金属表面层飞行时产生的感应电势，并借助于一种局域介电函数，分别推导出当离子平行于表面飞行及垂直于表面飞行时感应势的解析形式。数值结果表明，分子离子中离子之间相对距离的变化将对表面感应势的变化产生明显影响。     

The Influence of the Interaction Potential on the Diffusion of Neutral Particles in Oxyfluoride Glasses

A systematic study of the effects of the interaction potential upon the diffusion coefficients of neutral particles (P0s) and ions in the 60GeO₂–40PbF₂ glass has been performed using molecular dynamics simulations. The P0–P0 and P0–ions pair potentials were described by a Lennard–Jones potential with two parameters: the well depth (ε) and the size (σ). These parameters were varied in the ranges: (σ) = 0.1-1.0 eV and σ=1.0−4.0 ?. The diffusion coefficients were calculated for several combinations at several temperatures (300–1200 K). The estimated glass transition temperature (T _g) presented a slight dependence upon the potential parameters, but it is near the crystallization temperature of a glass of similar composition. Whereas, the diffusion coefficients of the P0s presented a strong dependence with the potential parameters, where increasing ε and σ causes a decrease of their diffusion coefficients. These results suggest that the atoms should be responsible for forming any surface film, since neutral particles larger than atom, such as, nanoparticles, should have negligible diffusion.     

Bond-order potential for transition metal carbide cluster for the growth simulation of a single-walled carbon nanotube

A classical many-body potential for transition metal carbide cluster is developed in the form of the bond-order type potential function. The parameter sets between carbon atoms and several transition metal atoms (Fe, Co and Ni) are constructed by fitting binding energies from Density Functional Theory (DFT) calculations. Using the potential function, clustering process of carbon atoms to a small metal cluster is studied by classical molecular dynamics (MD) simulation. The number of hexagonal rings in the Co cluster increases about twice as fast as in the Fe cluster. This implies that the graphitic lattice interacts more strongly with Co atoms than with Fe atoms. A Co cluster has a crystal structure where metal atoms are regularly allocated and embedded in the hexagonal carbon network in the simulation. In contrast, carbon atoms cover the entire surface in case of the Fe cluster. Additionally, the potential energy surface that a carbon atom feels from a 2D closed-packed facet is examined using a hypothetical FCC(1 1 1) facet of several transition metals. The potential energy minima are distributed on the hexagonal network showing the 2D closed-packed facet can be a template where a graphene is formed.     

Disordering of the Pb (110) surface

Molecular dynamics simulations incorporating a many-body glue model potential (GM) have been used to investigate the atomic structure and dynamics of the Pb (1 1 0) surface in the range from room temperature up to the bulk melting point. The main features of the surface disordering process include: generation of vacancies and the formation of an adlayer, the formation of so-called “local steps” and further their proliferation including wandering, creation and propagation of a quasiliquid surface film. These processes are illustrated by the use of a modern visualization technique.     

纳米TiO2表面电位特性的研究

纳米颗粒表面Zeta电位对颗粒的分散稳定性影响很大.本文研究了包覆SiO2前后的纳米TiO2在不同pH值条件下、不同溶剂(水、乙二醇、乙醇)以及不同离子浓度情况下的Zeta电位变化,并用质子迁移理论进行分析,为制备稳定的分散体系提供一定的理论指导.     

Interatomic potential for copper–antimony in dilute solid–solution alloys and application to single crystal dislocation nucleation

A new interatomic potential for copper–antimony (Cu–Sb) in low Sb concentration solid–solution alloys is proposed based upon the Lennard-Jones (LJ) pair formulation. Parameters for this new potential, σ and ε, are motivated by calculations of the Cu–Sb heat of solution (heat of mixing) and the strain field generated by a single substitutional impurity in single crystal copper, which is analyzed for impurity (dopant) atoms with various atomic radii. A well established embedded-atom method (EAM) potential is used to model the host copper. The ε parameter is derived for a range of values of σ by matching to the experimental value of the heat of solution. Then, the strain field around a single dopant atom is computed for each set of the calculated LJ parameters. Ultimately, the final parameters for the Cu–Sb interaction are selected to match the strain field corresponding to the atomic radius mismatch between Sb and Cu and are compared with the Eshelby solutions which are based on classical theory of elasticity. As an application of this new potential, it is shown using molecular dynamics simulations that the plastic deformation behavior of single crystal copper is affected by the characteristics of the strain field around the dopant atoms.     

An improved molecular dynamics potential for the Al-O system

Molecular dynamics (MD) simulations of aluminum oxide material and the aluminum oxidation process require a sufficiently sophisticated and well-calibrated potential, one that takes into account locally varying Al/O ratios and adaptive charge transfer between Al and O atoms. In this work we show that the Charge Transfer Ionic Potential (CTIP) by Zhou et al. [X.W. Zhou, H.N.G. Wadley, J.-S. Filhol, M.N. Neurock, Phys. Rev. B 69 (2004) 035402] in combination with a new, “Reference Free” version of the Modified Embedded Atom Method (RFMEAM) potential performs well for this purpose. This new potential has been parameterized by systematically fitting it to a large database of different Al_xO_y crystal energies, over a range of lattice constants and elastic deformations, using a recent method which separates the electrostatic and non-electrostatic fitting steps. The resulting potential yields more realistic atomic charges, crystal energies and lattice constants than earlier potentials. In particular, we show that the angular forces in the MEAM part are essential for α-Al₂O₃ to be the lowest-energy aluminum oxide. We compare the performance of our potential with the potential of Zhou et al., which lacks angular forces and was parameterized using a less involved fitting procedure, and show the results of a few molecular dynamics simulations. The two-step fitting method is generally applicable and can be adopted for constructing potentials for other metal-oxide systems.     

Effect of solvents on properties of the ultrasound assisted synthesized ceria nanoparticles and its performance as an adsorbent

The present study revealed a facile, ultrasound assisted ceria nanoparticle synthesis route by the reduction of cerium nitrate hexahydrate in different solvents at room temperature. The different solvents employed were methanol (MeOH), ethylene glycol (EG), water (aq) and isopropyl alcohol (IPA). The ceria nanoparticles were synthesized without the use of any capping agent in 20?min. The yield obtained was around 90% for the synthesized ceria samples. As synthesized ceria nanoparticles were characterized by X-ray diffraction (XRD), Field emission gun scanning electron microscopy (FEG-SEM), Brunauer Emmett Teller (BET) and zeta (ζ) potential in order to determine the influence of solvent on the physical properties of ceria nanoparticles. All the ceria samples illustrated a predominant spherical shape with the size in the range of 5–20?nm. It was found that interaction of the solvent with ceria nanoparticles in the presence of ultrasound plays an important role in modulating crystallite size, surface charge and its adsorption performance for a xylene milling yellow 6G dye. Among all the sonicated ceria samples, IPA mediated ceria exhibited highest positive zeta potential and hence was found to be proficient for the complete removal of dye in 15?min. Furthermore, the adsorption of the yellow milling dye on the surface of (IPA mediated) sonicated ceria sample has shown to follow pseudo-first order kinetic model. The non-sonicated sample (prepared in MeOH solvent without ultrasound) shows negligible dye adsorption while sonicated sample reveals 50% removal of XMY dye due to the difference in zeta potential values resulted from the cavitation effects.