Direct atomic structure determination of materials through computerised electron microscopy

The best performing high resolution electron microscopes (HREM) nowadays achieve an interpretable resolution of about 0.2 nm so that structural details of matter can be visualised almost up to the atomic scale. If a resolution of 0.1 nm could be reached, most of the individual columns of a structure could be resolved, which would make HREM an extremely useful technique for the study of new materials. However, the power of the technique is still severely limited by the problem of the interpretation of the images. Due to the complex imaging process, details in the observed images do not necessarily correspond to features in the structure of the objects. The only way to obtain reliable information is by comparing simultaneously the experimental images with computer simulated ones for known structure models. However, this trial and error technique requires a large amount of prior information obtained by other techniques. HREM would be much more powerful and independent if a direct method could be established to extract the structural information directly from the images in an automatic and quantitative way using a minimum of prior knowledge of the object under study. Such a method is described.