A computer program has been written for the purpose of standardizing crystal structure data according to rules formulated by Parthé & Gelato [Acta Cryst. (1984). A40, 169–183]. From input consisting of space‐group symbol, unit‐cell parameters and positional coordinates of the atoms, a reordered and renumbered list of standardized atom coordinates is obtained. The space group is now in the standard setting and the cell is reduced if applicable. The origin and the orientation of the coordinate system have been chosen in such a way as to minimize the standardization parameter Γ. A second standardization parameter, based on the position of the centre of gravity of the atoms in the asymmetric unit, is introduced. The Wyckoff sequence, obtained from the standardized structure data, can be used to recognize structures which are isopointal. An example of the application of STRUCTURE TIDY is given.

A computer program has been written with the aim of calculating powder patterns without the use of crystallographic tables. This has been achieved by deriving all symmetry information such as general equivalent positions from the Hermann-Mauguin space-group symbols, by calculating automatically the multiplicities of special positions and by storing the necessary constants, such as scattering factor tables, anomalous dispersion correction terms and X-ray wavelengths in the program. Owing to the very restricted amount of input data this program is especially suited for users with a limited knowledge of crystallography.

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This paper describes a proposal for a standardized presentation of inorganic crystal-structure data with the aim to recognize identical or nearly identical structures from the similarity of the numerical values of the atom coordinates.

Single crystal diffraction methods have been used to solve the crystal structure of Cu2CdGeS4: space group Pmn21 (C7v); a=7.692, b=6.555, c= 6.299 ,~i. Five other compounds of general composition 122464 also show superstructures either of wurtzite or of sphalerite, while the twenty investigated 122364 compounds have no ordered cation arrangement producing simple wurtzite or zincblende diffraction patterns.The problems in the determination of quaternary zincblende or wurtzite related superstructures in general are discussed.