A search–match system for X-ray powder diffraction data

Abstract

A computer program which can identify the crystalline component phases of a mixture from its X‐ray diffraction pattern is described. The program uses the data base of powder diffraction patterns maintained by the Joint Committee on Powder Diffraction Standards. The `reverse searching' technique employed permits the identification of each component and provides an estimate of confidence in the identification. Errors in measured spacings and intensities are tolerated by the program. The interactive search‐match system is available for general use via a networked timeshared computer.

Results and conclusions of the internet based “Search/match round robin 2002”

“…The computer programs were of the first generation, and the PDF contained 25 000 phases. Some more recent publications are concerned with the application of search/match software (for instance PDSM) to some of these round robin data (Marquart et al , 1979; Marquart, 1986), however, the mixtures were not unknown, and the program belongs to the second generation. Computer speed and user friendliness have changed enormously since these times.…”

X‐Ray Diffraction

“…In the mid-1960s, three main-frame computerbased search programs were described almost simultaneously. In the following years, each of the programs has been modified in some manner, either to improve operation, generalize the application, include many types of data files and computers, or incorporate successful features found in other search/match programs [8,9]. The program was called ZRD, because it uses atomic number Z, functional group information /?, and <i-spacing data D. Other computer programs were described by Johnson and Vand [6] and Nichols [7].…”

“…The rapid incorporation of minicomputers into diffraction instrumentation has provided a great opportunity to perform rapid data collection and sophisticated data reduction, followed by search/match procedures on an automated or semiautomated basis, completely in-house and unattended (see e.g., [12,13]). In the United States today more than 90% of all new powder diffractometers sold are automated to some degree, although still less than 10% or so of the 30000 diffraction users in the world are currently using computers for search/matching.…”

Environmental Uses of the NIH-EPA Chemical Information System

“…This contains the crystal lattice parameters for some 65,000 molecules and is useful for identifying a compound from its crystalline cell dimensions. There is also a file of 34,000 powder diffraction patterns (10). This data base, maintained by the Joint Committee on Powder Diffraction Standards, is very useful for identifying organic and inorganic materials.…”