测定微小晶体结构的电子晶体学图像处理技术

Electron crystallographic image processing techniques of structure determination for minute crystals

介绍了2005年国家自然科学奖二等奖获奖项目“微小晶体结构测定的电子晶体学研究”.研究目的是建立一种借助高分辨电子显微像测定晶体结构的新方法.为此提出了高分辨电子显微学与衍射晶体学相结合的思想,在实现此思想的过程中,研究了像衬的规律,得出实用的像衬公式和理论,阐明了不同种类原子像衬与晶体厚度的关系,而且用理论指导实验,观察到晶体中锂原子的像衬.以此理论为依据,把衍射晶体学中的多种分析方法特包是直接法引入到高分辨电子显微学中,建立了一套全新的电子晶体学图像处理技术,开发了相应的可视化专用软件包,并应用于测定多个未知晶体结构.文中逐一介绍了研究工作全过程的关键问题和研究结果.

The project ＂Electron crystallography study on the structure determination of minute crystals＂ that won a Second Class National Natural Science Award in 2005 is described. The aim of the research was to set up a new method of crystal structure determination by means of high-resolution electron microscope images. For this purpose an idea to combine high-resolution electron microscopy and diffraction crystallography was proposed. To realize this idea the principles of image contrast were investigated, a practical equation of image intensity was derived and the corresponding image contrast theory developed. The variation of image contrast with crystal thickness for different kinds of atoms was elucidated. This led to the successful observation of the image contrast of lithium atoms. Based on this theory various analysis methods developed in diffraction crystallography were introduced into high-resolution electron microscopy, and a completely new technique named electron crystallographic image processing was established. This technique has been utilized to determine the structure of several new crystals, and a corresponding special visualized software package has been developed. An overview of the key points and results obtained in the project are presented.