A Modified Fourier Technique in Crystal Structure Analysis

Abstract
A modified Fourier synthesis can be made modifying each of the coefficients by a weight 1-exp {-b(sin θ/λ)2}. Characteristic properties of the modified Fourier syntheses are given. It is found that in practice the parameter b ranging from 30 to 10 is useful for structure determination when Cu Kα is used. An application of this technique to the structure determination of δ-pyrazinamide is given, where this technique is proved to be useful in distinguishing oxygen from nitrogen and nitrogen from carbon. An application to difference synthesis is also discussed.