用密度泛函理论研究金属表面吸附产生的电子空穴谱
Electron-hole spectra created by adsorption on metals from density-functional theory
摘要：
吸附在金属表面上的非绝热性引起许多可测量的效应，例如化学电流和外电子发射。在这里，我们提出了一个定量理论的基础上的基态密度泛函理论（DFT）计算的有效电子势和Kohn-Sham能带结构的化学电流。激发概率计算电子空穴对和电子和空穴分别从一阶含时微扰理论。这是通过评估后续（静态）DFT计算之间的有效电子势的变化率的矩阵元素（Kohn-Sham状态之间）来实现的。我们的方法与电子摩擦理论有关，但允许直接访问激发光谱。该方法被应用于原子氢同位素在Al（111）表面的吸附。结果与现有的实验数据（贵金属表面）是兼容的，特别是，所观察到的同位素效应H与D吸附本理论描述。此外，结果是在定性的协议与计算详细的计算的全动力学内的时间相关的密度泛函理论，与显着的例外，由于自旋动力学的影响。作为一个微扰的方法，这里提出的方法是足够简单，适用于广泛的一类吸附物和表面，而在同一时间，让我们提取系统特定的信息。
英文摘要：
Non-adiabaticity in adsorption on metal surfaces gives rise to a number of measurable effects, such as chemicurrents and exo-electron emission. Here we present a quantitative theory of chemicurrents on the basis of ground-state density-functional theory (DFT) calculations of the effective electronic potential and the Kohn-Sham band structure. Excitation probabilities are calculated both for electron-hole pairs and for electrons and holes separately from first-order time-dependent perturbation theory. This is accomplished by evaluating the matrix elements (between Kohn-Sham states) of the rate of change of the effective electronic potential between subsequent (static) DFT calculations. Our approach is related to the theory of electronic friction, but allows for direct access to the excitation spectra. The method is applied to adsorption of atomic hydrogen isotopes on the Al(111) surface. The results are compatible with the available experimental data (for noble metal surfaces); in particular, the observed isotope effect in H versus D adsorption is described by the present theory. Moreover, the results are in qualitative agreement with computationally elaborate calculations of the full dynamics within time-dependent density-functional theory, with the notable exception of effects due to the spin dynamics. Being a perturbational approach, the method proposed here is simple enough to be applied to a wide class of adsorbates and surfaces, while at the same time allowing us to extract system-specific information.
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