The calculation of ε associated with normalized structure factors, E

A method is presented for the convenient computation of the quantity ε used for obtaining the values of normalized structure factor magnitudes from structure factor amplitudes, ε has the value of unity for general reflections but can take on integral values which differ from unity for special classes of reflections. The method is based on the application of rotation operators which are easily formed from knowledge of the equivalent positions for the space group of interest. Only general positions are considered. Proof is given here for the procedure which has been used heuristically in the program system titled XRAY72.