A New Direct Method of Indexing Single Crystal X-ray Photographs - The "Tilted Crystal" Method

The detailed X-ray investigation of single crystals of low symmetry by the interpretation of rotation and oscillation photographs taken on stationary films may often be difficult because trial and error methods of indexing are required, and considerable overlapping of X-ray reflexions may occur. A direct method of indexing X-ray reflexions on this type of photograph is described. It is based on the interpretation of the exact positions of the X-ray reflexions produced by a crystal rotating or oscillating about a direction which is slightly inclined to a crystallographic axis. The principles, the mathematical basis and the applications of the new method are discussed relative to other methods available. The tilted crystal method may also be used for obtaining information about crystal symmetry.