An ab initio molecular dynamics and correlation function approach to dissipative adsorbate vibrational spectroscopy

固体表面附近的原子或分子的振动是表面科学的核心。通过稳态和时间分辨光谱探测振动提供了“指纹”，这有助于我们理解表面的基本过程，并从控制和优化它们的角度出发。理论上对吸附物振动的分析通常基于简正模分析（NMA），其不考虑非谐性、温度、模式耦合和光谱信号。他们通常也忽略“耗散”，即， 由耦合到表面声子和电子空穴对（EHP）激发引起的弛豫，尽管这可以对光谱具有决定性影响。在这个项目中，我们将超越NMA通过使用和扩展从头算分子动力学（AIMD）和AIMD与电子摩擦（AIMDEF）方法，结合时间相关函数（TDCF）的分析和表面吸附物的振动光谱。这些方法考虑了上述的所有效应，给出了实时信息，具有扩展到包括量子效应的潜力，并且可以在“飞行”模式下操作，而不需要预先计算势能面。这使得它们适用于很难以其他方式处理的复杂系统。具体而言，我们的目标是在一个现实的振动-声子和/或振动-EHP耦合及其对振动光谱的影响建模，红外（IR）和振动和频（VSF）光谱，稳态和时间分辨。要考虑的系统是氢覆盖的硅表面、水覆盖的金属和金属氧化物表面以及与烃接触的金属表面。

The vibrations of atoms or molecules near solid surfaces are central to surface science. Probing the vibrations by steady-state and time-resolved spectroscopy provides "Fingerprints" which facilitate our understanding of elementary processes at surfaces, with the perspective to control and optimize them. The analysis of adsorbate vibrations by theory is often based on Normal Mode Analyses (NMA), which do not account for anharmonicity, temperature, mode couplings, and spectroscopic signals. They typically neglect also "Dissipation", i.e., relaxation caused by coupling to surface phonons and Electron Hole Pair (EHP) excitations, despite this can have a decisive influence on spectra. In this project we will go beyond NMA by using and extending Ab Initio Molecular Dynamics (AIMD) and AIMD with Electronic Friction (AIMDEF) methods, in combination with Time-Dependent Correlation Functions (TDCFs) for analysis and vibrational spectroscopy of adsorbates at surfaces. These methods account for all effects of above, give real-time information, have the potential to be extended to include quantum effects, and can be operated in an "on the fly'' mode without the need to precompute potential energy surfaces. This makes them applicable to complex systems which can hardly be treated otherwise. Specifically, we aim at a realistic modelling of vibration-phonon and / or vibration-EHP couplings and their influence on vibrational spectra, InfraRed (IR) and Vibrational Sum Frequency (VSF) spectra, both steady-state and time-resolved. Systems to be considered are hydrogen-covered silicon surfaces, water-covered metal and metal oxide surfaces, and metal surfaces in contact with hydrocarbons.