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首页> 外文期刊>Physical review >Geometric and electronic structure of commensurate 4Ar/Ag(111)-(7~(1/2) X 7~(1/2))R19.1° by density functional theory
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Geometric and electronic structure of commensurate 4Ar/Ag(111)-(7~(1/2) X 7~(1/2))R19.1° by density functional theory

机译：密度泛函理论研究相应的4Ar / Ag（111）-（7〜（1/2）X 7〜（1/2））R19.1°的几何和电子结构

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We report the optimization of a 4Ar/Ag(111)-(7~(1/2) X 7~(1/2))R19.1° monolayer using first-principles density functional theory. The adsorption energies resulting from our ground-state minimizations are similar for all three anchor sites. A commensurate adsorbate cell is comprised of four argon atoms which settle into three different configurations. We refer to these sites as top, threefold hcp hollow, and threefold fcc hollow sites. Each of these structures has one Ar atom located at one of the base sites of the Ag(111) surface. The remaining three Ar atoms are found near the bridge sites of the silver surface. In both of the hollow site structures, the bridge locations are measurably off of the exact geometric bridge positions while maintaining the 7~(1/2)R19.1° unit cell. Our results show that both the hcp and fcc hollow sites have slightly lower adsorption energies than the top site, by only 1.5 and 4.5 meV, respectively (per cell of four Ar atoms). The vertical harmonic vibration frequencies were computed for the top, hcp, and fcc hollow sites. They measured 5.22, 5.01, and 5.21 meV, respectively. We studied the possible cause for this high-order commensurate monolayer. We have concluded that neither steric repulsion nor hybridization of the electrons of the Ar atoms is the reason for the commen-surability in our model. We propose that the causal mechanism is the Novaco-McTague [Phys. Rev. Lett. 38, 1286 (1977)] theory for orientational epitaxy.
机译：我们使用第一原理密度泛函理论报告了4Ar / Ag（111）-（7〜（1/2）X 7〜（1/2））R19.1°单层膜的优化。我们的基态最小化所产生的吸附能对于所有三个锚点都相似。相称的吸附池由四个氩原子组成，这些氩原子沉降成三种不同的构型。我们将这些站点称为顶部，三重hcp空心和三重fcc空心站点。这些结构中的每一个都有一个位于Ar（111）表面的碱基之一上的Ar原子。在银表面的桥位附近发现了其余三个Ar原子。在这两个中空场地结构中，桥的位置都可测量地偏离精确的几何桥位置，同时保持7〜（1/2）R19.1°的晶胞。我们的结果表明，hcp和fcc空心位点的吸附能均比顶部位点略低，分别只有1.5和4.5 meV（每四个Ar原子）。计算了顶部，hcp和fcc空心位置的垂直谐波振动频率。他们分别测量了5.22、5.01和5.21 meV。我们研究了这种高阶相称单分子层的可能原因。我们得出的结论是，在我们的模型中，无论是空间排斥力还是Ar原子电子的杂化都不是可比性的原因。我们提出因果机制是Novaco-McTague [Phys。牧师38，1286（1977）]定向外延理论。

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