On the beam selection and convergence in the Bloch-wave method

Bloch-wave theory has been a popular tool for simulating electron diffraction patterns for quantitative analysis, such as determination of atomic positions and structure factors. However, up to now no investigations have been published concerning the convergence of this method. In particular it is quite unclear how many and which beams should be included in simulations. Beams are often manually selected in a rather subjective manner. In this paper, three simple criteria for selecting the beams automatically are examined. These criteria can easily be incorporated into existing Bloch-wave programs. Some examples showing the power of this technique are given. Computation experience shows that these three parameters can be manipulated independently to achieve convergence.