Electron diffraction analysis using a personal computer

Abstract

The analysis of electron diffraction patterns (EDPs) by manual calculation is difficult in two important cases. The first is when there are many phases that must be included in the search for a pattern’s solution. The second is when, due to the structure of the phases being considered, many solutions for a pattern are possible. In these cases, it is very time consuming to ensure that all possible solutions are found and that the best solution is chosen. A computer can provide tremendous help for the EDP analyst in these situations. Through its ability to make rapid calculations and display data graphically, a computer can relieve the analyst of much of the work involved in a thorough electron diffraction analysis.In analyzing EDPs a standard procedure is adopted. The analyst first assembles a data base of phases that could be present in the sample being studied. Tables of interplanar spacings and interplanar angles are calculated from crystal structure data on each phase. The positions of spots on experimental patterns are then recorded and radii from the transmitted beam spot to diffracted beams’ spots are measured. Ratios of radii and angles between radii are tabulated.