Current status of the IUCr powder intensity project

The eventual objective of powder intensity measurements, in the present context, is to obtain absolute integrated Bragg intensities from specimens which are ideal with respect to all parameters such as extinction, preferred orientation, etc. At present, the Project has been limited to a comparison of X-ray techniques on a number of samples of carbonyl process nickel which are known to be non-ideal, but which were determined by actual measurement to yield identical integrated intensities using Cu Kα radiation. Eleven samples have been measured in ten laboratories and six of these have been standardized by measurement of the incident beam. The results show that integrated intensities may not be relied on to better than 5%, even on a relative basis. It appears that, at the present time, the techniques for making an accurate measurement of the incident beam may be more reliable than those for measuring relative intensities.