Calculation of Structure Factors and Summation of Fourier Series in Crystal Analysis: Non-centrosymmetrical Projections

Abstract

Two useful methods for carrying out these operations have recently been described in NATURE. The Fourier synthesis reduces to summing series of the type ₁ and ₂ being co-ordinates in a projection of the structure, expressed as fractions of the cell sides. In the method described by C. A. Beevers and H. Lipson¹, strips of numbers are printed giving all the values of A cos h₁ from A = + 99 to A = 99, h = 0 to h = 20, and ₁ at 6° intervals from 0° to 90°, the latter 15 numbers being printed in a row along the strip. The synthesis then reduces to selecting the correct strips, placing them over each other, and adding up the columns of numbers.