General IBM360 Computer Program for Determining the Multiplicities of Crystal Forms, to Be Used in Conjunction with the Rietveld Powder Profile Refinement Program

摘要

An IBM 360 computer program has been written which generates multiplicity data for the crystal forms in any space group. The input data consist of the unit cell dimensions, lattice centring indicator, system type, equivalent positions of the space group, and the range of h, k, l and 2 theta. The program calculates structure factors for all reflexions over the powder pattern, and sorts them into forms using the IBM OS sort/merge progrm. The form indices (hkl) are taken as those of the last member of the form generated and the multiplicity m(hkl) as the number of reflexions encountered through the form. The (hkl), m(hkl) data serve as input for the Rietveld powder profile refinement program for the refining of structural parameters with powder data. Previously, these had to be deduced from the International tables for X-ray cyrstallography Volume 1, which is difficult to use with the higher symmetry systems. As the (hkl) and multiplicity generation is a major part of the effort needed to set up the Rietveld program, the present program reduces significantly the work involved in these refinements. The program gives ((hkl), m(hkl)) cards in about 3-50 seconds of CPU time. (Atomindex citation 09:384692)