Quantitative electron microdiffraction

The uses and significance of the ground state charge density distribution in crystals are reviewed. Methods for measuring this quantity quantitative transmission electron microdiffraction are discussed, based on accurate measurement of structure factor amplitudes and phases. It is demonstrated that the effect of 5at% doping on convergent beam electron diffraction (CBED) intensities is easily measured, and the effect of doping by Mn at this level on gamma TiAl is studied and the implications for mechanical properties are discussed. The significance of the mean electrostatic potential is reviewed in terms of surface effects and bulk bonding. Phase determination using overlapping coherent CBED orders is reviewed, the deleterious effects of multiple scattering are emphasised, and the symmetry properties of the resulting patterns are analysed.