广义簇合物在非均匀几率密度下的生长

采用族合物生长的自调整模型，并用扩散粒子的非均匀几率密度场模拟了簇合物和扩散粒子之间的非均匀相互作用势场,研究了广义簇合物在非均匀场下的生长形态，考察了深度因子α、粘附参数t等对簇合物生长形态及对非均匀场的影响，结果表明，非均匀场的性质是决定族合物生长几何形态的主要因素，深度因子α决定了簇合物中生长形态的紧密程度，粘附参数t决定了致密程度，α、t等参数对场的作用有一定的影响     

Teo的C~2模型与其它稠合规则之间关系的研究

提出了一个稠合型簇合物的稠合规则,讨论了唐氏拓扑结构规则和Mingos稠合规则的推广,扩大了两个稠合规则的应用范围.研究了在稠合型簇合物中Teo的C2模型与Mingos稠合规则、推广的唐氏拓扑结构规则和本文提出的稠合规则之间的关系.同时,利用提出的稠合型簇合物的稠合规则导出了超级簇合物"clusters of clusters"中原子和电子之间存在的魔数关系.     

聚合物稳定的金簇合物上卤素吸附质：质谱检测及其对催化的影响

聚(N-乙烯基-2-吡咯烷酮)稳定的金簇合物(Au：PVP)的质谱结果表明,来源于合成前驱体的Cl吸附质主要存在于Au34和Au43簇合物上。金簇合物上Cl吸附质的数量不影响其催化有氧苯甲醇氧化性能,表明Cl原子与Au簇合物间存在较弱的键合作用。相反,用Br替代Au34和Au43簇合物上Cl显著抑制了其催化活性,但对其电子结构没有任何影响。这表明, Br原子与金簇合物的键合较强,在空间上堵塞了活性位。因Br吸附质而导致活性显著下降表明, Au34和Au43簇合物对Au：PVP催化活性起主要贡献。     

多中心d—pπ键与高氧化态钼簇合物的几何构型（I）“碎片结构”模型及分子轨

本文通过对不同构型的二核钼簇合物簇胳结构的分子轨道计算,揭示了Mo-B（T）原子间的多中心d-pπ键与该结构的稳定性及结构参数a,q和之间的内在联系，提出了2－6核高氧化态钼簇合物的簇胳由“碎片结构”组合而成的设想，该模型对以u2-S2为桥的三桥钼簇合物中的“共面－异面”规划的和簇胳为[Mo3S3O]^6 的钼簇中的反[常Mo-Mo键距级出合理解释，确认了桥原子对Mo-Mo键长和键强的决定作用。     

Cu_4簇合物“元件组装”合成及其结构与电催化作用

以元件组装方法合成了Cu4(HL)4·2H2O簇合物(H2L=N-乙氧羰基-N′-o-硝基苯基硫脲)。用X射线单晶衍射技术、核磁共振谱、红外光谱和元素分析等确定了簇合物及其相应组装元件的晶体结构和化学组成,并对簇合物的电催化性质进行了检测。结果表明,该簇合物由4个Cu(I)以M-M键构成簇核,4个硫脲配体分别以硫羰基硫原子和氮原子配位于Cu(I)构成簇合物配位结构,DPV分析显示该簇合物对O2具有较高催化活性。     

「VS_4-Cu_n」簇合物的固相合成、结构规律和成簇机理的研究

以(NH_4)_3VS_4为起始原料与CuCl在低温团相不同反应条件下,得到了不同簇骼的[VS_4-CU_n]的簇合物,并总结了CuCl/(NH_4)_3VS_4不同摩尔比、不同反应温度和时间对簇合物生成的影响和[VS_4-Cu_n]簇合物的结构规律.同时探索了V-Cu-S簇合物固相合成的成簇机理.     

多中心d-pπ键与高氧化态钼簇合物的几何构型——(Ⅰ)“碎片结构”模型及分子轨道研究

本文通过对不同构型的二核钼簇合物簇胳结构的分子轨道计算,揭示了Mo—B(T)原子间的多中心d-p π键与该结构的稳定性及结构参数α、θ和R之间的内在联系,提出了2～6核高氧化态钼簇合物的簇胳由“碎片结构”组合而成的设想,该模型对以μ_2-S_2为桥的三核钼簇合物中的“共面—异面”规则和簇胳为[Mo_4S_3O]~(6+)的钼簇中的反常Mo—Mo键距给出合理解释,确认了桥原子对Mo—Mo键长和键强的决定作用。     

电喷雾多级串联质谱法研究碱金属硝酸盐和亚硝酸盐簇合物离子的裂解行为

在正常毛细管温度(200 ℃)下,利用电喷雾质谱(ESI-MS)研究了NaNO3、KNO3、NaNO2和KNO2形成的新型簇合物离子,采用电喷雾多级串联质谱(ESI-MSn)研究了簇合物离子裂解行为.实验结果表明: NaNO3和KNO3溶液产生的簇合物离子及这些离子的裂解方式相似;NaNO2溶液产生的簇合物离子比NaNO3和KNO3溶液产生的复杂;KNO2溶液产生了含有Na+离子的簇合物离子,通过分析KNO2簇合物离子的裂解行为证明了Na+与NO-2的亲合势大于K+.此外,还研究了离子源金属毛细管温度和溶液浓度对簇合物离子形成的影响.     

聚合物稳定的金簇合物上卤素吸附质:质谱检测及其对催化的影响（英文）

聚(N-乙烯基-2-吡咯烷酮)稳定的金簇合物(Au:PVP)的质谱结果表明,来源于合成前驱体的Cl吸附质主要存在于Au_(34)和Au_(43)簇合物上.金簇合物上Cl吸附质的数量不影响其催化有氧苯甲醇氧化性能,表明Cl原子与Au簇合物间存在较弱的键合作用.相反,用Br替代Au_(34)和Au_(43)簇合物上Cl显著抑制了其催化活性,但对其电子结构没有任何影响.这表明,Br原子与金簇合物的键合较强,在空间上堵塞了活性位.因Br吸附质而导致活性显著下降表明,Au_(34)和Au_(43)簇合物对Au:PVP催化活性起主要贡献.     

金属羰基簇合物对二茂铁间电荷传递的阻断和增强

本文通过三种二茂铁基金属羰基簇合物的循环伏安特性,研究了金属羰基簇合物对二茂铁间电荷传递的影响.其中钴羰基簇合物对二茂铁间的电荷传递有阻断作用,而锇羰基簇对二茂铁基的电荷传递有增强作用。研究表明羰基簇与共轭炔桥的配位形式决定增强和阻断的根本原因。     

Nucleation,growth, and fractal dimensions of icosahedral and polyicosahedral clusters

In this paper, the concept offractal geometry was applied to the growth of icosahedral and polyicosahedral clusters. Fractal dimensions were calculated for high-frequency icosahedral casters, vertex-sharing polyicosahedral clusters, and linked polyicosahedral clusters. These cluster growth pathways were compared with the fractal growth mechanisms of colloidal particles. Close similarities were found despite the tremendous differences in particle sizes and the forces governing their nucleation and growth processes.Dedicated to Prof. Lawrence F. Dahl on his 65th birthday; based in part on a lecture presented by BKT at the Dahl symposium held at the University of Wisconsin, Madison, Wisconsin on September 17, 1994.     

Growth of PtRu Clusters on Ru(0001)‐Supported Monolayer Graphene Films

We report on results of a detailed scanning tunnelling microscopy study on the formation, size and size distribution, and internal structure of small bimetallic PtRu clusters on a graphene monolayer film supported on a Ru(0001) substrate. These clusters, with sizes around ～15 (Ru) or ～40 (Pt) atoms per cluster at the lowest coverage, are interesting model systems for the catalytic behaviour of small metal PtRu particles, for example for application in electrocatalytic oxidation reactions. The clusters were generated by sequential deposition of the two metals at room temperature. The data reveal a distinct influence of the deposition sequence on the cluster formation process, with Ru pre‐deposition followed by Pt deposition leading to predominantly bimetallic clusters, possibly with a core–shell‐type structure, while the reverse sequence results in co‐existent mono‐ and bimetallic clusters, where the latter are likely to intermix at the interface. The observations are related to the nucleation process of the respective metals on the templated surface, and the 2D growth behaviour of the two metals.     

Reductive growth of nanosized ligated metal clusters on silicon nanowires

The reductive growth of metal clusters on silicon nanowires (SiNWs) is reported. The HF-etched SiNWs were found to reduce ligated Au-Ag clusters of single size, shape, composition, and structure. In the process, the surfaces of the SiNWs were reoxidized. The reductive cluster growth on the SiNW surface was followed by high-resolution transmission electron microscopy (HRTEM). The reduced metal clusters grew to different sizes in the nanometer regime (1-7 nm in diameter) on the SiNW surfaces. At sizes greater than approximately 7 nm, they tend to separate from the SiNW surfaces. Further growth and/or agglomeration of these colloidal particles to sizes greater than roughly 25 nm in diameter eventually causes the particles to precipitate from solution. Two interesting phenomena, the "sinking cluster" and the "cluster fusion" processes, were observed under TEM.     

Molecular dynamics study of the catalyst particle size dependence on carbon nanotube growth

The molecular dynamics method, based on an empirical potential energy surface, was used to study the effect of catalyst particle size on the growth mechanism and structure of single-walled carbon nanotubes (SWNTs). The temperature for nanotube nucleation (800-1100 K), which occurs on the surface of the cluster, is similar to that used in catalyst chemical vapor deposition experiments, and the growth mechanism, which is described within the vapor-liquid-solid model, is the same for all cluster sizes studied here (iron clusters containing between 10 and 200 atoms were simulated). Large catalyst particles, which contain at least 20 iron atoms, nucleate SWNTs that have a far better tubular structure than SWNTs nucleated from smaller clusters. In addition, the SWNTs that grow from the larger clusters have diameters that are similar to the cluster diameter, whereas the smaller clusters, which have diameters less than 0.5 nm, nucleate nanotubes that are approximately 0.6-0.7 nm in diameter. This is in agreement with the experimental observations that SWNT diameters are similar to the catalyst particle diameter, and that the narrowest free-standing SWNT is 0.6-0.7 nm.     

Detailed model of the aggregation event between two fractal clusters

A model has been developed for describing the aggregation process of two fractal clusters under quiescent conditions. The model uses the approach originally proposed by Smoluchowski for the diffusion-limited aggregation of two spherical particles but accounts for the possibility of interpenetration between the fractal clusters. It is assumed that when a cluster diffuses toward a reference cluster their center-to-center distance can be smaller than the sum of their radii, and their aggregation process is modeled using a diffusion-reaction equation. The reactivity of the clusters is assumed to depend on the reactivity and number of their particles involved in the aggregation event. The model can be applied to evaluate the aggregation rate constant as a function of the prevailing operating conditions by simply changing the value of the particle stability ratio, without any a priori specification of a diffusion-limited cluster aggregation, reaction-limited cluster aggregation, or transition regime. Furthermore, the model allows one to estimate the structure properties of the formed cluster after the aggregation, based on the computed distance between the aggregating clusters in the final cluster.     

High nuclearity metal clusters: Miniature bulk of unusual structures and properties?

Recent developments in cluster synthesis have produced many high nuclearity metal clusters of discretesize andshape approaching that of small particles. Some of these clusters have metal arrangements resemblingfragments of metallic lattices and thus may be considered as aminiature bulk. Some are related to the quasicrystalline phase. Yet others have little or no structural features in common with that of the bulk. These metal clusters of definitivesize andshape provide an opportunity for the study of the evolution of band structure fromatomic tomolecular to thebulk. The focus of this review is on the unusual structures and properties of well-defined high nuclearity metal clusters and their possible relations or variant to the bulk state. Specifically, interesting electronic, optical, and magnetic properties of metal clusters in the quantum-size regime are described. Structural systematics of high nuclearity metal clusters, ranging from thecluster-of-clusters to thelayer-by-layer growth sequence, are discussed. It is hoped that further studies of the structures and properties of large metal cluster compounds of discretesize andshape will shed light on how, when, and why metallic or other bulk behavior begins and ends.     

Characterization of large supported metal clusters by optical spectroscopy

Small sodium and silver particles were generated on dielectric substrates like LiF, quartz and sapphire under ultrahigh vacuum conditions. The optical transmission spectra of the clusters were measured as a function of cluster size and shape, for low and high substrate temperatures as well as for s- and p- polarization of the incident light. Excitation of dipolar surface plasmon oscillations in the directions normal and parallel to the substrate surface could be identified. Furthermore, optical spectra for Na and Ag clusters were calculated with the classical Mie theory. The measured spectra vary strongly if the experimental conditions are changed and can be exploited, for example, to characterize the particles with regard to their size and shape. In particular, the axial ratio of the spheroidal clusters could be determined. Its value is considerably different for the two investigated metals and depends on the substrate material. Furthermore, the temperature of the substrate has a pronounced influence on the shape of the particles. At low temperature of T=100 K two-dimensional island growth is predominant. The particles extend only little in the direction perpendicular to the surface and coalesce readily at small coverage of metal atoms. In contrast, the clusters are truly three-dimensional at T=300 K. At this stage, sodium particles still exhibit a rather small axial ratio whereas silver clusters appear almost spherical. Thus, measurements of the optical spectra permit direct in situ monitoring of cluster growth during the nucleation of adsorbed atoms and of temperature induced shape variations. In addition to investigations of the shape of the particles, the quadrupolar surface plasmon mode was observed for Ag clusters.     

A Study About Nanocluster Deposition of Thin-film Formation by Molecular Dynamics Simulation

The thin-film growth has been confirmed to be assembled by an enormous number of clusters in ICBD method. In sequence of clusters’ depositions proceeds to form the thin-film to understand quantitatively the interaction mechanisms between the cluster atoms and the substrate atoms, we use molecular dynamics simulation with EAM potential. The quantitative of flatness of deposition and percent of disordered atoms were proposed to evaluate the property of thin-film. In this simulation, three different Co cluster sizes of 55, 70, and 100 atoms with different velocities (100 up to 800 m/s) were deposited on a Al(0 0 1) substrate whose temperatures were set between 300 and 500 K. The simulations begin at specific equilibrium temperature of clusters and the substrate. The simulations are performed at different temperatures of the clusters and substrate and for different sizes of clusters. We showed that the percent of disordered atoms of substrate are affected by the cluster size and velocity of the clusters. Temperature dependence of the number of disordered atoms for different cluster’s velocity was observed. We investigated the effect of cluster size and initial velocity of cluster on the value of flatness.     

Cluster-cluster aggregation controlled by the number of intercluster connections: kinetics of aggregation and cluster mass frequency

The aggregation of colloids in the presence of hydrodynamic forces was investigated, employing a numerical model that took into account the masses of the individual clusters and the number of intercluster connections established when two clusters stuck together. The number of possible connections was determined by analyzing all the possible nonoverlapping configurations of stuck clusters. This operation was done for a couple of clusters of various masses, taking into account the assembly of clusters of even and uneven masses. The formulation of the constraints established a certain hierarchy in the sticking on a basis compatible with the irregular fracture model of Horwatt and co-workers. As a result, the permanent sticking of large clusters required the formation of a large number of connections, whereas that of small clusters might be realized even with a small number of connections. Thus, the aggregation started with the features of the standard reaction-limited process and this cluster growth became progressively inhibited as a result of the prevailing effects of the connection constraints. The cluster-mass frequency showed the emergence at least of a second population whose bell-shaped mass distribution was superimposed on the monotonically decreasing distribution resulting from the reaction-limited aggregation process. The results of the numerical study were confronted with those previously obtained in the aggregation of hydrated polystyrene latex particles dispersed in 1 M sodium chloride solution. The two striking features--the aggregate growth kinetics and the mass distribution function--were common to the computer-generated clusters and the latex aggregates.