Approximations for dynamical calculations of microdiffraction patterns and images of defects

The calculation of dynamical elastic diffuse electron scattering from a crystal containing a point defect or dislocation may require prohibitively large amounts of computing time. Two approximations are described which greatly reduce the computer time required for these calculations, and so allow the simulation of electron-microscope images of defects at atomic resolution. The diffuse scattering expected from microdiffraction experiments can also be predicted in this way.