Sven Hovmöller and Xiaodong Zou
Electron crystallography opens up new possibilities for crystal structure determination
besides the traditional techniques of X-ray and neutron diffraction. Electron
diffraction gives similar kind of data as X-ray and neutron diffraction, but from
crystals millions of times smaller. A unique advantage of using electrons is that they
(in contrast to neutrons and X-rays) can be focused to an image in the electron
microscope. In high resolution electron microscopes (HREM) it is possible to see
structures down to the level of single atoms. The crystallographic structure phases
which are lost in X-ray diffraction (the phase problem) can be determined experimentally
from the Fourier transform of HREM images.
We are developing methods and theory for electron crystallography.
Electron microscopy images are often distorted so that an immediate interpretation in
terms of atomic structure is not possible. These distortions are caused by for example
crystal misalignment, wrong focus and astigmatism. We have developed image processing
methods for estimating and correcting for all these distortions.
In collaboration with the Russian programmers Maxim Larine and Slava
Klimkovitch, we have developed the computer program systems CRISP for crystallographic
image processing, ELD for quantitative analysis of electron diffraction patterns.
References (many of these papers can be downloaded from http://www.mmk.su.se/~svenh/index.html: