Surface Structure of Oxides

非技术描述：从更节能的催化剂到新型电子设备，氧化物表面对于科学和技术领域都越来越重要。目前，人们对氧化物表面的结构还不够了解，无法预测哪种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，以及它们如何与气体物种反应。然后，开发的工具可以被其他正在设计涉及这些系统的接口的人使用，或者正在探索它们在新的燃料电池、更高效的水分解催化剂或衬底上的用途，以在其上生长基于氧化物的新型电子设备。技术细节：所采用的策略将扩展的密度泛函理论(DFT)方法(包括精确交换杂化)和键价化学概念结合在一起，采用实验-理论结合的方法，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法和衍射法来解决表面结构。除了对发现的表面结构使用DFT方法外，研究小组正在扩大已发表的原子位置数据库和键价方法的测试，方法是在原子位置的完整细节无法公开的其他氧化物表面上进行计算。另一个组成部分是开发DFT和相关优化代码的算法，特别是准牛顿法。用于DFT的软件已经被整合到一个大型软件包中，供全球1800多个组织使用(www.numis.northwestern.edu)。在教育方面，作为现有计划的一部分，这项研究有助于支持当地对高中生的推广，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).