(HP-97) … Calculating Cell Parameters in Electron & X-Ray Diffraction

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An extract from Programs for Calculating Cell Parameters in Electron & X-Ray Diffraction, NASA, Technical Paper 1529, 1979 (54 pgs.)

SUMMARY
Ten programs for calculating cell parameters from single-crystal electron diffraction patterns are presented. Most of the programs, written for use with a programmable desk calculator, are also applicable to x-ray diffraction work. The programs can be used to calculate d-spacings from electron diffraction plate measurements, and to determine cell data (including interplanar angles and zone angles) for all crystal systems. A program for rhombohedral-hexagonal conversions and one for matching crystal data from standards with apparent crystal parameters found in diffraction patterns are included. Because they allow rapid determination of data not present in x-ray listings or elsewhere in the literature, the programs facilitate identification of unknowns. Full understanding of the programs requires some knowledge of crystal structure and familiarity with programming the HP-97 calculator. The programs are easy and inexpensive to use compared to the time required on large computers. Furthermore, data appear immediately so that results are available continuously while working on a problem …

DESCRIPTION OF PROGRAMS
The programs listed here range from simple (Program 1: calculation of camera constant and d spacings in electron diffraction patterns) to complex (Program 9: determination of triclinic crystal-system parameters) …
Program 10 involves calculation of apparent crystallographic parameters, such as may be observed in diffraction patterns of nonorthogonal crystals, from the known parameters of standard compounds …
For full understanding of the programs, some familiarity with crystal structure and electron or x-ray diffraction is required. Although the programs were designed for use with an HP-97 calculator, workers with some knowledge of the style of programming used can perhaps adapt the program steps to other units.

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