Electron crystallographic image processing techniques of structure determination for minute crystals

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.