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Metallic clusters on a model surface: Quantum versus geometric effects

机译：模型表面上的金属团簇：量子效应与几何效应

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摘要

We determine the structure and melting behavior of supported metallic clusters using an ab initio density-functional-based treatment of intracluster interactions and an approximate treatment of the surface as an idealized smooth plane yielding an effective Lennard-Jones interaction with the ions of the cluster. We apply this model to determine the structure of sodium clusters containing from 4 to 22 atoms, treating the cluster-surface interaction strength as a variable parameter. For a strong cluster-surface interaction, the clusters form two-dimensional (2D) monolayer structures; comparisons with calculations of structure and dissociation energy performed with a classical Gupta interatomic potential show clearly the role of quantum shell effects in the metallic binding in this case, and evidence is presented that these shell effects correspond to those for a confined 2D electron gas. The thermodynamics and melting behavior of a supported Na_(20) cluster is considered in detail using the model for several cluster-surface interaction strengths. We find quantitative differences in the melting temperatures and caloric curve from density-functional and Gupta treatments of the valence electrons. A clear dimensional effect on the melting behavior is also demonstrated, with 2D structures showing melting temperatures above those of the bulk or (at very strong cluster-surface interactions) no clear meltinglike transition.
机译：我们使用从头算密度函数为基础的团簇内相互作用和表面近似处理作为理想的光滑平面，确定与簇离子产生有效的Lennard-Jones相互作用的过程，来确定支持的金属簇的结构和熔融行为。我们应用该模型来确定包含4至22个原子的钠簇的结构，并将簇表面相互作用强度作为变量参数。对于强烈的团簇表面相互作用，团簇形成二维（2D）单层结构。与经典Gupta原子间电势进行的结构和解离能计算的比较清楚地表明，在这种情况下，量子壳效应在金属结合中的作用，并且证据表明这些壳效应与受限的二维电子气相对应。使用几个簇表面相互作用强度的模型，详细考虑了支持的Na_（20）簇的热力学和熔融行为。我们发现价电子的密度函数和古普塔处理在熔化温度和热曲线上存在定量差异。还显示了对熔化行为的明显尺寸影响，其中二维结构显示的熔化温度高于整体温度或（在非常强的团簇表面相互作用下）没有明显的类似熔化的转变。

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  • 来源
    《Physical review》 |2011年第7ptab期|p.075430.1-075430.9|共9页
  • 作者

    S. A. Blundell; Soumyajyoti Haldar; D. G. Kanhere;

  • 作者单位

    SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054, France;

    Centre for Modeling and Simulation, University of Pune, Ganeshkhind, Pune411 007, India,Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India;

    Department of Physics, University of Pune, Ganeshkhind, Pune 411 007, India;

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  • 正文语种 eng
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  • 关键词

    structural transitions in nanoscale materials;

    机译：纳米级材料的结构转变;

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