Surface Structure of Oxides

非技术描述：氧化物表面在科学和技术领域越来越重要，从更节能的催化剂到新型电子设备。目前对氧化物表面结构的了解还不够，无法预测哪种类型的材料最适合未来的需求。该项目正在开发工具，以了解氧化物表面的结构，以及它们如何与气态物质发生反应。这些开发出来的工具可以被其他人使用，他们正在设计涉及这些系统的界面，或者正在探索它们在新型燃料电池、更有效的水分解催化剂或生长新型氧化物电子设备的基质中的应用。技术细节：所采用的策略结合了扩展密度泛函理论（DFT）方法，包括精确交换杂化和键价化学概念，结合实验-理论方法，利用一些独特的超高真空（UHV）电子显微镜设备。主要的实验工具是透射电子显微镜成像和衍射来求解表面结构。除了对发现的表面结构使用DFT方法外，研究小组还通过对原子位置的完整细节尚未公开的其他氧化物表面进行计算，扩大了已发表的原子位置和键价方法测试的数据库。一个额外的组成部分是开发DFT算法和相关的优化代码，特别是准牛顿方法。DFT软件已经被整合到一个大型软件包中，被全球1800多个团体使用（www.numis.northwestern.edu）。在教育方面，这项研究有助于支持本地高中生作为现有项目的一部分，以及更多涉及通用公共许可证（GNU）软件电子直接方法（edm）的国际努力。

NON-TECHNICAL DESCRIPTION: Oxide surfaces are increasingly important for both scientific and technological areas ranging from more energy-efficient catalysts to new types of electronic devices. Currently not enough is understood about the structure of oxide surfaces to predict what type of materials will be best for future needs. This project is developing tools to understand both the structure of oxide surfaces, as well as how they react with gaseous species. The tools that are developed can then be used by others who are designing interfaces involving these systems, or are exploring their use in new fuel cells, more efficient water-splitting catalysts or substrates upon which to grow new types of oxide-based electronic devices.TECHNICAL DETAILS: The strategy employed combines extended density-functional theory (DFT) methods including exact-exchange hybrids and the bond-valence chemical concepts in a combined experimental-theoretical approach exploiting some unique ultra-high vacuum (UHV) electron microscopy facilities. The main experimental tools are transmission electron microscopy imaging and diffraction to solve the surface structures. In addition to using DFT methods for the surface structures found, the research team is expanding the database of published atomic positions and tests of the bond-valence approach by performing calculations on other oxide surfaces where full details of the atomic positions are not publically available. One additional component is developing algorithms for DFT and related optimization codes, particularly quasi-Newton methods. The software for DFT has already been incorporated into one large package used by more than 1800 groups around the world (www.numis.northwestern.edu). In terms of education, the research helps support both local outreach to high-school students as part of existing programs, as well as more international efforts involving the general public license (GNU) software electron direct methods (edm).