MODIFICATION OF THE MULTISLICE METHOD FOR CALCULATING COHERENT STEM IMAGES

Based on the Schrodinger equation, the multislice method is derived in a new way which is more appropriate for calculating coherent STEM images. It is shown that the effects of beam tilt can be included in two equivalent ways which are convenient for different purposes of application. It is shown that, if the coherent STEM probe is considered as a superposition of many tilted plane waves, one cannot use the traditional multislice formulae for each tilted beam, since this leads to the loss of phase information which can be important for coherent many-beam illumination. The new formulations lead to a faster procedure for coherent STEM image simulations. Advantages of the proposed procedure are discussed with respect to a few different illumination conditions.