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The microstructure of materials and measurements of imperfections ranging from point defects and short-range disorder on the nanometer scale to residual stress and texture effects on the macroscopic scale are the focus of Newsletter 24 of the IUCr Commission on Powder Diffraction. Topics addressed include residual stress in thin layers (Welzel, Leoni, Lamparter and Mittemeijer) and individual grains (Poulsen and Kvick), size and size-strain effects in line broadening (Langford and Ungar), low-resolution and high-resolution diffraction experiments (Fewster), local and long-range order (Billinge, Petkov and Proffen) and modeling of microstructure in Rietveld refinement (Popa, Scardi, Leoni and Dong). Current microstructural analysis benefits from more accurate modeling techniques and significant improvements in radiation sources. Many of today's Rietveld-refinement programs can handle effects of texture line shift and broadening at an advanced level, which allows determination of pole figures, orientation-distribution functions, residual elastic stress/strain tensors, and locally varying lattice strains. The interdependence of sophisticated analysis methods, fast computers, and advanced instrumentation, is stimulating rapid advances in knowledge about the microstructure of materials.

D. Balzar (CPD News, No. 24, 2000)

Reference Materials: The certification of two new Standard Reference Materials (SRMs) by NIST will be of interest to powder diffractionists. The SRM640c (Silicon powder) and SRM660a (LaB6 powder) standards will be valuable to Line Profile Analysis (LPA) and for the testing of instrumentation and methods. Applications and methodological developments in Powder Diffraction will be the subject of forthcoming meetings on Accuracy in Powder Diffraction III (Gaithersburg, MD, USA, April 22-25, 2001) and Size-Strain III (Trento, Italy, Dec. 2-6, 2001).

Powder Commission Officers (1999-2002). Chairman: P. Scardi (paolo.scardi@ing.unitn.it); Secretary: A.N. Fitch (fitch@esrf.fr); R. Delhez (Netherlands), S.P. Sen Gupta (India), R.B. Von Dreele (USA), D. Balzar (USA), G.J. Kruger (S. Africa), H. Fjellvåg (Norway), W.I.F. David (UK), R.E. Dinnebier (Germany).

CPD Projects: Information on the current status of the CPD projects is available at www.iucr.org/iucrtop/comm/cpd/projects/index.html. Size/Stain Round Robin: www.boulder.nist.gov/div853/balzar/s-s_rr.htm. Quantitative Phase Analysis Round Robin: www.iucr.org/iucr-top/comm/cpd/QARR/index.html.

P. Scardi (CPD News, No. 24, 2000)