Back to the Beginning

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Back to the Beginning

X-ray diffraction was first demonstrated in 1912, and the advent of powder diffraction followed soon after. Between then and the 1930's powder diffraction was commonly being used as an identification tool but only in a "local sense". It was not until Hanawalt, Rinn and Frevel, of the Dow Chemical Company, published in 1938 a database file of about 1000 powder diffraction patterns (Ind. Eng. Anal. Ed., 1938, 10, 457-512) under the auspices of the American Society for Testing and Materials (ASTM) that the idea really caught the imagination (though more limited files had previously been published by A.N.Winchell in 1927 and A.W.Waldo in 1935). Since then the database has grown and changed ownership and name several times (e.g. the ASTM in the 1940's; the Joint Committee on Powder Diffraction Standards (JCPDS) in the 1970's). The current guardians are the International Centre for Diffraction Data (ICDD) based in the state of Pennsylvania, U.S.A. (see external links).

The current experimental file comprises in the region of 100000 entries, which contain much useful information in addition to the powder diffraction pattern, and indeed the file is often used in a non-diffraction sense; for instance, as a source for values of physical properties of a material, such as density. The original database consisted of a set of cards, one card for each material plus its powder diffraction pattern parameters (see later). In 1962, the d, I values, plus the formulae and PDF index number were recorded as a computer-readable database. The latter became known as PDF-1. In the 1970s, the full card index, still based around d and I values, became available, and this is now known as PDF-2. Today all or parts of the file may be purchased in the form of books, microfiche, magnetic tape or CD-ROM, at costs ranging from <$1000 to <$10000 depending on need.

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