报告题目：粉末衍射和微区衍射在哪里相遇?
Where do powder diffraction and microdiffraction meet?
报告人姓名：Catherine DEJOIE
报告时间：2016-01-14 13:45
报告地点：上海大学宝山校区东区材料学院B楼526会议室
报告人简介(中文)：2016-… 欧洲同步辐射中心,线站科学家 2012-2015 瑞士苏黎世高工,博士后 2009-2011美国洛伦兹-伯克利国家实验室,博士后 2006-2009 法国尼尔研究所,博士报告人单位(中文)：欧洲同步辐射中心报告人单位(英文)：European Synchrotron Radiation Facility, France
报告内容简介：Structural characterization of polycrystalline materials is usually performed using powder diffraction techniques. Indeed, the crystals may not be large enough be studied using conventional single-crystal methods, or they may be unsuitable for other reasons. For example, the crystals may not be of sufficient quality for single-crystal data collection, they may be embedded in a heterogeneous matrix, or they may be in a constrained environment (e.g. during an in situ experiment). In such cases, powder diffraction techniques are usually applied, and indeed over the last two decades these methods have developed to the point that quite complex structures can be solved and refined in an almost routine manner [1]. However, in some difficult cases, the powder condition cannot be achieved, or single crystal information is required. Then, alternative methods have to be devised. I will present two examples related to the structure analysis of polycrystalline materials. In the first example, the structure of the indigo@silicalite pigment, an analog of ancient Maya Blue was determined by combining X-ray Laue microdiffraction and powder diffraction techniques [2]. Laue microdiffraction was used to map the unit cell changes (and thereby the indigo distribution) within a single crystal and to retrieve the most probable space group. With this information, the indigo@silicalite structure could be solved and refined from the powder diffraction data. In my second example, I will present an alternative method for studying polycrystalline materials developed in collaboration with the Swiss Free-electron Laser Project. Using a non-monochromatic beam (4% energy bandpass), the reflection intensities of stationary crystals can be measured reliably. If a unique diffraction pattern of many randomly oriented crystals can be recorded and processed, a complete analysis of the crystal structure will be possible from a single snapshot [3]. Potential applications for in situ time-resolved studies will be discussed.
