IUCr 1999 Triennial Report - Commission on Small Angle Scattering

The Commission was chartered at the Seattle Congress. During the three years since its inception this Commission has focused on three topics: (1) community building, (2) education, and (3) standardisation.

A web site (http://www.nist.gov/sas) has been built to serve as a 'community centre'. The associated list server (sa_scat@nist.gov) has attracted a fairly steady subscribership of 300+ individuals. The message traffic has been sparse, but many readers have found it to be a valuable resource for getting questions answered and activities publicised.

The series of triennial world congresses established in 1965 has long been a core component of the small-angle scattering (SAS) community. 1999 is the occasion for the eleventh such congress (see http://sas99.bnl.gov/sas99). This will serve as a formal occasion for obtaining feedback and enhanced participation from the members of the community.

On the education front there has been a more or less steady series of workshops and organised sessions at national meetings. The Commission has worked with the American Crystallographic Association, the Society of Plastics Engineers, and the American Chemical Society in these efforts. These activities are aimed at increasing awareness of SAS methodologies in the broader world of materials science. Dates and titles are available in the Commission's Annual Reports for the relevant years.

It will be an uphill struggle for the Commission to get standardised SAS methodologies accepted into the community. The tradition of quantitative characterisation of the performance of test methods is weak. Indeed, many users do not understand the concept of a 'SAS test method'. There is no widespread set of software tools for reducing and visualising SAS data. There has been very little work devoted to putting data derived from different realisations of SAS experiments onto a common basis.

An interlaboratory test program for SAXS measurements in the moderate q range (0.1 nm^—1 < q < 3 nm^—1) is in the design stages. We are soliciting suggestions for suitable samples for use in a comparable effort for SANS. We hope that the results from such objective assessments of test method performance will stimulate a desire for more rigorous approaches to these matters.

The Commission has taken some tentative steps in the direction of improved standardisation by issuing a draft CIF for one-dimensional SAS data. We have been supporting other efforts to develop suitable standards for two- and three-dimensional SAS data. The hosts of software tool collections are being encouraged to expand their activities.

By increasing the awareness of SAS users, by promulgating appropriate standards, and by facilitating the development of appropriate analytical methods, the Commission hopes to help our little corner of crystallographic science realise its full potential.

The Commission would like to thank M. Hart and H. Fuess for their efforts on our behalf in their roles as liaison to the Executive Committee. The support of P. Coppens and W.L. Duax as we worked to establish the Commission and develop its agenda is also appreciated.

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