Image simulation in electron microscopy

Abstract

The theoretical calculation of High Resolution Transmission Electron Microscope (HRTEM) images has become a routine operation due largely to the existence of several commercially available computer programs. Associated with these “black box” calculations, exists a danger coming from the ease with which the programs can be used to produce images without any understanding of the underlying physical principles and approximations used in the calculations. While hopefully the majority of users of image simulation take the care to understand the limitations of the technique, there are several basic principles that must be understood in order to use the technique within the limits of its applicability. An example of this is shown in figure 1.Although image simulation is fairly straightforward, and the technique has been applied successfully to many problems in HRTEM, figure 2, it is not an optimum tool for solving unknown structures. Each image depends on many adjustable parameters, the structure itself being the most important, and the task of computing hundreds of images and comparing them visually is a tedious task to say the least.