The Development of a Standard for Single Crystal Diffractometer Alignment. Certification Of Ruby Spheres as a Standard Reference Material. W. Wong-Ng¹, T. Siegrist², H. Evans³, E. Gabe⁴, G. Enright⁴, G. DeTitta⁵, L. Finger⁶, M. Kirisits⁵ and J. Armstrong¹, ¹NIST, Gaithersburg, MD 20899, ²Lucent Technologies, Murray Hill, NJ, ³US Geological Survey, Reston, VA, ⁴SIMS, NRC, Ottawa, Canada, ⁵Hauptman-Woodward Medical Research Institute, Buffalo, NY, ⁶Geophysical Laboratory, Washington DC

A lattice parameter standard is critical for accurate single crystal structural studies. An international joint effort is underway to produce a standard reference material (SRM) for this purpose. This SRM material is based on a set of ruby spheres (Cr-doped alumina). It is intended to improve the accuracy of lattice parameter determinations, and to assess the X-ray technique and the state of the instrument employed at each local laboratory. This paper discusses the progress of the certification process. Results include quantification of the Cr content, measurement of lattice parameters using single crystal diffractometers and the powder Guinier-Hagg method, and the determination of the mosaic structure of the ruby spheres assessed by triple crystal spectrometry. In addition, the spheres are part of an international round-robin project involving 50 crystallographic groups worldwide. The results of the round robin will be discussed.