First-principles investigation of the quantum-well system Na on Cu(111)
First-principles investigation of the quantum-well system Na on Cu(111)
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DOI：
10.1103/physrevb.61.13973
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发表时间：
2000-05
影响因子：
3.7
通讯作者：
J. Carlsson;B. Hellsing
中科院分区：
文献类型：
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作者：
J. Carlsson;B. Hellsing
从理论上研究了Cu（111）上的碱金属吸附体系Na，以澄清光发射实验中观察到的量子阱态的可能存在。我们分析了体系的位点偏好、成键特性、功函数的覆盖依赖性和电子结构。该研究基于真空中独立Na层、清洁Cu（111）表面和两种不同吸附结构（$(2\ifmmode\times\else\texttimes\fi{}2)$和$(3/2\ifmmode\times\else\texttimes\fi{}3/2).$）下Na/Cu（111）吸附体系的第一性原理计算。我们能够识别Na诱导的能带，这些能带基本上定位在Cu（111）表面的局部带隙中。这些波段中最低的$\overline{\mathrm{\ensuremath{\Gamma}}}$点的局部态密度在Na层内达到最大值，并迅速衰减到衬底中。na诱导能带的色散与光发射数据吻合良好，最低na诱导能带的$\overline{\ensuremath{\Gamma}}$点能量从$(2\ifmmode\times\else\texttimes\fi{}2)$结构的费米能级以上0.45 eV转移到饱和单层结构的费米能级以下0.06 eV。我们得出结论，na诱导态具有量子阱态的特征，这支持了先前基于光电实验的解释。
The alkali-metal adsorption system Na on Cu(111) has been investigated theoretically in order to clarify the possible presence of quantum-well states observed in photoemission experiments. We analyze the site preference, bonding character, the coverage dependence of the work function, and the electron structure of the system. The study is based on first-principles calculations of free-standing Na layers in vacuum, the clean Cu(111) surface, and the Na/Cu(111) adsorption system at two different adsorbate structures: $(2\ifmmode\times\else\texttimes\fi{}2)$ and $(3/2\ifmmode\times\else\texttimes\fi{}3/2).$ We are able to identify Na-induced bands, which are essentially localized in the local band gap of the Cu(111) surface. The local density of states at the $\overline{\mathrm{\ensuremath{\Gamma}}}$ point for the lowest of these bands has maxima within the Na adlayer and decays rapidly into the substrate. The dispersion of the Na-induced bands is in good agreement with photoemission data and the $\overline{\ensuremath{\Gamma}}$ point energy of the lowest Na-induced band shifts from 0.45 eV above the Fermi level for the $(2\ifmmode\times\else\texttimes\fi{}2)$ structure to 0.06 eV below the Fermi level for the saturated monolayer. We conclude that the Na-induced states have the characteristics of quantum-well states, which supports previous interpretations based on photoemission experiments.