Hull stated “That every crystalline substance gives a pattern that the same substance always gives the same pattern and that in a mixture of substances each produces its pattern independently of the others, so that the photograph obtained with a mixture is the superimposed sum of the photographs that would be obtained by exposing each of the components separately for the same length of time. In 1938, Hanawalt, Rinn, and Frevel were the first to report tabulated data on diffraction patterns of 1000 chemical substances they also gave a scheme of classification which made possible a routine and valuable use in the chemical laboratory of the Hull method of x-ray analysis which was published in 1919. In the late thirties, the powder x-ray diffraction technique was recognized as a powerful technique for phase identification/chemical analysis. This article summarizes information concerning the JCPDS-ICDD organization, the Powder Diffraction File (PDF), history and accomplishments of the JCPDS-ICDD Research Associateship. In addition, various research collaborations with NBS/NIST also led to the development of several standard reference materials (SRMs) for instrument calibration and quantitative analyses, and computer software for data collection, calibration, reduction, for the editorial process of powder pattern publication, analysis of powder data, and for quantitative analyses. As a result of this collaboration, more than 1500 high quality powder diffraction patterns, which have had a significant impact on the scientific community, were reported. The PDF is a continuing compilation of patterns gathered from many sources, compiled and published by the ICDD. The main mission of the Associateship was to publish high quality x-ray reference patterns to be included in the Powder Diffraction File (PDF). The Research Associateship program of the Joint Committee on Powder Diffraction-International Centre for Diffraction Data (JCPDS-ICDD, now known as the ICDD) at NBS/NIST was a long standing (over 35 years) successful industry-government cooperation.
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