First Principle Calculation on AunAg2 （n = 1 - 4） Clusters

The first-principles method based on density-functional theory is used to investigate the geometries of the lowest-lying isomers of AunAg2 （n = 1 - 4） clusters. Several low-lying isomers are determined, and many of them in electronic configurations with a high spin multiplicity. The stability trend of Ag-doped Aun dusters is compared to that of pure Aun clusters. Our results indicate that the inclusion of two Ag atoms in the clusters lowers the cluster stability, indicating higher stability as the structures grow in size. The bigger energy difference between the Aun and AunAg2 curves as the structures grows in size. This information will be useful to understanding the enhanced catalytic activity and selectivity gained by using silver-doped gold catalyst.     

Magnetic properties of the cyclic spincluster Fe6:bicine

The magnetic properties of the cyclic compound [Fe₆(bicine)₆] LiClO₄ ^. 2MeOH are reported. The cluster Fe₆(bicine)₆ forms an antiferromagnetically coupled ring structure of Fe ^III ions. The magnetic susceptibility is measured between 2 and 300 K and yields the exchange coupling of J/k _B = - 27.5±0.5 K. The field dependence of the magnetic moment is studied at 3 and 6 K in magnetic fields up to 5 T. The zero-field splitting of the first excited spin states with S = 2 and 3 are determined by ESR at 94 GHz. The intra-molecular interactions of the Fe ^III ions are analyzed and the on-site anisotropy of the Fe ^III due to the ligand-configuration is determined to d /k _B = - 0.633±0.008K. Received 28 October 2002 / Received in final form 22 February 2003 Published online 20 June 2003 RID="a" ID="a"e-mail: bernd@piobelix.physik.uni-karlsruhe.de     

Interpretive approach to collective effects of electrons in multicenter problems

Interpretive theoretical tools prove valuable in guiding the analysis of experiments in the realm of atomic clusters. Here, we review basic elements of an analytic approach that makes it possible to find and visualize the effective electrostatic potential and Coulomb correlations in multicenter problems. To illustrate the utility of these concepts we apply them to exploring molecular-doped metallic clusters. This study is aiming at a systematic, visual assessment of changes induced in screening, Coulomb correlation and effective potential by varying the charge of the electronegative impurity and its position in the cluster cage.     

钠原子团簇的相变

采用紧密结合的分子动力学模型，对Ｎａ４、Ｎａ８、Ｎａ２０的结构特性进行了分析。通过对这些钠原子团簇的键长涨落和径向密度分布的分析，发现在２００Ｋ到２５０Ｋ的温度范围内有从类固相到类液相的改变     

Different self-avoiding walks on percolation clusters: A small-cell real-space renormalization-group study

We calculate the average number of stepsN for edge-to-edge, normal, and indefinitely growing self-avoiding walks (SAWs) on two-dimensional critical percolation clusters, using the real-space renormalization-group approach, with small H cells. Our results are of the formN=AL ^D _SAW+B, whereL is the end-to-end distance. Similarly to several deterministic fractals, the fractal dimensionsD _SAW for these three different kinds of SAWs are found to be equal, and the differences between them appear in the amplitudesA and in the correction termsB. This behavior is atributed to the hierarchical nature of the critical percolation cluster.     

Wn(n=3—27)原子团簇结构的第一性原理计算

使用密度泛函理论下的第一性原理方法，对W_n原子团簇(n=3—27)的结构特性进行了理论计算. 得到了W_n团簇(n=3—7)的最低能量结构和(n=8—27)的局域能量极小的典型结构. 使用凝胶模型，提出的电子组态1s²1p⁶1d¹⁰2s²1f¹⁴2p⁶3s     

嵌入La和Gd原子的Si24笼团簇的稳定性

用梯度修正自旋极化密度泛函(DFT)电子结构计算,研究了具有T_h和D_2d对称性包裹La和Gd原子的Si₂₄富勒烯的稳定性.结果表明Gd@Si₂₄具有很高的磁性而La@Si₂₄的磁性完全猝灭.这些结果有可能导致Si基富勒烯团簇新的结构类型. 关键词： 24和Gd@Si₂₄包裹团簇')" href="#">La@Si₂₄和Gd@Si₂₄包裹团簇 自旋极化密度泛函 稳定性 电磁性质     

Effect of sulphur doping on manganese clusters: an ab initio study

We report a structural, electronic and magnetic analysis of minimal Mn_nS clusters, n = 1–13, from ab initio calculations. Total geometry optimizations were performed by considering compact manganese clusters, doped with a single sulphur atom. The doping was added to the cluster by considering substitution, interstitial and adsorbed positions. To further investigate the influence of the sulphur doping on the magnetic properties of manganese clusters, we performed non collinear magnetic calculations within the local spin density approximation (LSDA) for the exchange-correlation. We find that the electronic properties can be better controlled when the cluster is doped with a sulphur atom, and less size dependent. There are no differences in the magnetic properties of doped and non-doped clusters, except for n=7 and 8, in which the total magnetic moment per atom are smaller in doped clusters.     

第一性原理对GanP-m阴离子团簇结构及其光电子能谱的研究

本文利用密度泛函理论(DFT)对GanP-(n=2-7)和GanP2-(n=1-6)阴离子团簇的几何结构、电子态及稳定性进行了研究.在B3LYP/6-31G*水平上进行了结构优化和频率分析,得到了GanP-(n=2-7)和GanP2-(n=1-6)团簇的基态结构.这些阴离子团簇的几何结构随着n的增大,在n=5时由平面结构转化为立体结构;在GanP2-(n=1-6)团簇中,P-P比Ga-P容易成键;在GanP-(n=2-7)和GanP2-(n=1-6)阴离子团簇中,Ga3P2-,Ga4P2-,Ga5P2-和Ga6P-的基态结构最稳定.