The Interpretation and Application of Electron-Diffraction `Kikuchi-Line' Patterns - Part I. The Determination of the Crystal Unit Cell, its Orientation and the Crystal Symmetry

The interpretation of electron-diffraction Kikuchi-line patterns from single crystals is developed as a powerful independent and general means of determining the crystal lattice type, dimensions and orientation and the Laue symmetry of the atomic arrangement. This aim is realized by a construction of the reciprocal lattice by methods which are described and illustrated. The satisfactory accuracy of the method is due to the relatively precise definitions for the location of the Bragg reflection positions, derived and stated here for the first time, which enable the method to be used even when the crystal lattice constants are large so that the bands are narrow and diffuse-edged, as with rhombic sulphur. The patterns shown also illustrate features of the line intensities, especially the reduction in intensity when the bands pass near the undeflected-beam spot.