Direct Methods for Surface Crystallography

尽管电子衍射技术已经成功地揭示了固体表面的许多详细结构，但早期的试错法在应用于日益复杂的表面结构和成分方面受到限制。 PI提出了改进的直接算法的发展的基础上，全息方法分析电子衍射实验结果。 计划与来自威斯康星-密尔沃基大学和埃尔兰根-纽伦堡大学的研究人员合作，进行光电子全息术、低能电子衍射、反射和透射高能电子衍射等实验工作。 计划与慕尼黑大学的实验工作合作，开发表面x射线衍射的直接算法，以确定表面层的整个三维电荷密度。就像光学全息术可以生成物体的三维图像一样，从表面散射的电子束可以用来生成原子及其在材料表面的伴随电子电荷密度的全息图像。 本研究提案的目的是开发更好的数学算法，用于将实验数据解码成这样的图像，并计划与使用各种电子散射技术的实验人员合作。 这些方法对于基础研究很重要，但对于从催化到腐蚀的表面关键应用尤其重要。

9815092SaldinAlthough electron diffraction techniques have been successful at revealing many of the detailed structures of solid surfaces, earlier trial-and-error approaches are limited in their application to increasingly complex surface structures and compositions. The PI proposes the development of improved direct algorithms based on a holographic approach for analyzing electron diffraction experimental results. Collaboration with experimental efforts are planned involving photoelectron holography, low energy electron diffraction, and reflection and transmission high energy electron diffraction with researchers from Wisconsin-Milwaukee and the University of Erlangen-Nuernberg. Additional work is planned in the development of direct algorithms for surface xray diffraction to determine the entire three-dimensional charge density of the surface layers, collaborating with experimental work at the University of Munich.%%%Much like optical holography can generate three-dimensional images of objects, electron beams scattered from surfaces can be used to generate holographic images of atoms and their accompanying electron charge densities at the surfaces of materials. The object of this research proposal is to develop better mathematical algorithms for decoding experimental data into such images, and collaborative work with experimentalists using a variety of electron scattering techniques is planned. These methods are important for basic research, but are particularly important for surface-critical applications ranging from catalysis to corrosion.***