Computer Simulation of Electron Microscope Images from Atomic Structure Models

ABSTRACTIt is generally the case that simple direct interpretation of high resolution electron microscope images is not possible due to the phase contrast imaging modes necessary to achieve atomic level spatial resolution. Therefore, an extensive number of computer programs have been developed to perform electron diffraction and image computations. Both single scattering or dynamical scattering processes can be simulated as well as any form of imaging mode currently available on most modern high performance transmission electron microscopes. Since one is interested in imperfections rather than perfect crystal structures, a large number of sampling points in real and reciprocal space are required. Often, large atom position arrays must be sampled requiring large mainframe computer memories and fast CPU's. High quality displays are also required for realistic image representations and even faster computational methods via television rate digital frame store devices. This paper will be centered about a number of materials areas requiring high resolution electron microscopy computer simulation from atomic structure models. These areas include: organometallic molecules, point defects, surface structure and reconstructions, amorphous thin films, quasi-crystals, semiconductor interfaces and grain boundary structure in metals.