Ab initio Structures from Powder Data

C. Giacovazzo, M. Czugler and H. Schenk in Bordeaux, August 1990. (Photo WLD)

When only powder data are available, crystal structure solution is still a difficult job. Overlapping of reflections, preferred orientations, background estimations, and several other geometrical and physical factors complicate the phasing process, and the structure solutions are often difficult. Personal experience with crystal data suggests that the creation of a data bank of powder data could play a central role for the advancement of crystal structure solution methods.

The bank should include: (a) data collected by synchrotron and neutron radiation as well as X-ray diffractometers, in order to provide problems produced by different resolution of experimental devices and types of radiation; (b) a variety of space groups, including those for which systematic overlapping of reflection occurs; (c) a variety of experimental techniques; and (d) a variety of detectors.

Anyone wanting to contribute to such a bank should supply the complete intensity pattern collected, information about experimental techniques, space group, refined cell parameters, the atomic positions and thermal parameters, the structure resolution approach, and relevant references.

I hope the IUCr Commission of Powder Diffraction would actively support this proposal either by direct management or by entrusting it to another body.