Simulating Surface Spectroscopy of Single Atom Magnets and Catalysts

用于催化和磁光应用的功能材料通常包含贵重材料，其稀缺性是最大化其使用效率的强烈动机。单原子可以作为催化剂（单原子催化剂，SAC）或单原子磁铁（SAM），当稳定在明确的基板。SAC/SAM材料常采用X射线光电子能谱和X射线吸收谱进行研究，但其丰富的结构和重叠的特征使这些谱线难以分离。该项目将开发新的模拟方法来预测这种复杂的光谱特征，并与实验合作伙伴合作，对新型SAM和SAC材料进行表征。用于催化和磁光应用的功能材料通常含有珍贵材料，其稀缺性是最大限度地提高其使用效率的强烈动机。这可以通过降低贵金属原子的浓度，同时保留或甚至改善其作为反应中心或磁性中心的功能来实现。在极端情况下，当稳定在明确定义的基底上时，单原子可以作为催化剂（单原子催化剂，SAC）或单原子磁体（SAM）。[1，2] X射线光电子能谱（XPS）、X射线吸收光谱（XAS）和X射线磁性圆二色性（XMCD）在表征稳定的单个原子的结构、电子和磁性状态方面起着重要作用。实验XPS和NEXAFS光谱中存在的丰富结构和重叠特征通常对所有峰的明确归属提出挑战。在这里，电子结构和芯能级跃迁的理论分析和计算模拟可以产生新的见解。基于第一性原理的芯能级光谱模拟已经建立[3]，然而，几乎所有实用的电子结构方法都只能可靠地预测源自1 s态激发的光谱。在实验上，单个金属原子的电子和磁性状态最好通过探测具有较高角动量的核心状态来表征，例如2 p，3d或4f型轨道，这仍然缺乏模拟技术。在这个项目中，您将开发一种有效但近似的方法来模拟2 p，3d和4f状态的核心水平光谱，这对于分析SAM和SAC的化学和磁性状态是重要的。在与实验伙伴的合作中，新方法将被应用于理解具有高磁矩的表面支撑单原子的X射线光谱实验。新的方法将开发一个既定的电子结构软件包结合国家的最先进的自旋轨道耦合，强相关性，和核心孔的限制的方法。

Functional materials for catalysis and magnetooptical applications often contain precious materials, the scarcity of which is a strong motivation for maximizing the efficiency of their use. Single atoms can act as catalysts (Single atom catalysts, SACs) or single atom magnets (SAMs) when stabilized on well-defined substrates. SAC/SAM materials are often studied with X-ray photoelectron spectroscopy and X-ray absorption spectroscopy, but the rich structure and overlapping features make these spectra hard to disentangle. This project will develop new simulation methodology to predict such complex spectroscopic signatures and, in collaboration with experimental partners, novel SAM and SAC materials will be characterized.Functional materials for catalysis and magnetooptical applications often contain precious materials, the scarcity of which is a strong motivation for maximizing the efficiency of their use. This can be achieved by reducing the concentration of precious metal atoms while retaining or even improving their functionality as reactive or magnetic centres. In the extreme limit, single atoms can act as catalysts (Single atom catalysts, SACs) or single atom magnets (SAMs) when stabilized on well-defined substrates. [1,2]X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD) play an important role in characterizing the structure, electronic and magnetic state of stabilized single atoms. The rich structure and overlapping features present in experimental XPS and NEXAFS spectra often provide a challenge to the unambiguous assignment of all peaks. Here, the theoretical analysis and computational simulation of the electronic structure and core-level transitions can yield new insights. The first-principles-based simulation of core-level spectra is established [3], however, almost all practical electronic structure methods can only reliably predict spectra originating from excitation of 1s states. Experimentally, the electronic and magnetic states of single metal atoms are best characterized by probing core-states with higher angular momentum, such as 2p, 3d or 4f-type orbitals, for which simulation techniques are still lacking.In this project, you will develop an efficient but approximate methodology to simulate core-level spectra of 2p, 3d and 4f states, which are important for the analysis of the chemical and magnetic state of SAMs and SACs. In collaboration with experimental partners, the new methods will be applied to understand X-ray spectroscopy experiments on surface-supported single atoms with high magnetic moments. The new methods will be developed within an established electronic structure software package by combining state-of-the-art methods for spin-orbit coupling, strong correlation, and core-hole constraints.