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Numerical Control X-Ray Powder Diffractometry

Published online by Cambridge University Press:  06 March 2019

R. W. Rex
R. W. Rex*
Affiliation:
Chevron Research Company La Habra, California
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Abstract

Recent development of numerical control, N/C, systems for digital X-ray powder diffractometry opens the full potential for rapid and detailed machine processing of digital diffraction data. This capability may prove to be as large an incremental technological advance as the earlier shift from film to counter detector techniques. Our N/C system has the capability of performing essentially all operations possible by manual methods. Data output is on magnetic tape and carries identification, and some of the instructions necessary for processing. The data tapes are processed by programs that (a) edit and check, (b) filter through a controlled shape high frequency filter (square, triangular, normal, etc.), (c) remove the minimum background from the diffraction pattern, (d) analyze data points close to background and test for statistical significance deleting those points within limits defined to constitute noise, (e) recognize peaks and record their position and intensity, (f) identify phases, (g) calculate phase concentrations by various methods, including internal standard and mutual standard techniques, and (h) output any desired portion of the data in a variety of digital and analog formats suitable for display, further analysis, and storage in an information retrieval system.

It is possible to record an entire diffraction pattern for a phase on two or three inches of magnetic tape. This record carries detailed peak area and shape information now missing from the ASTM reference system. Furthermore, the new magnetic tape information is directly amenable to computer processing to prepare search oriented record systems of diffraction data that can be inexpensively updated and edited. Currently, an ASTM committee is preparing a magnetic tape format diffraction pattern file. It is suggested that a second generation, computer index system be generated based on digital records of actual diffraction patterns. This type of system should prove more versatile than the old system and possibly be the only way to keep abreast of the flood of new diffraction pattern information generated from the vast number of new organic and inorganic compounds being synthesized.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 10: Fifteenth Annual Conference on Applications of X-ray Analysis, August 10-12, 1966 , 1966 , pp. 366 - 373
Copyright
Copyright © International Centre for Diffraction Data 1966

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References

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