ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Accurate values of the absolute integrated reflections from a powder sample of Ni have been determined from measurements with synchrotron radiation as a function of scattering angle over a range of energies from 290 to 3 eV below the Ni K-absorption edge, 8332 eV. From these values, the dispersion factor f' has been determined by comparison of the experimental scattering factors with the theoretical values of Wang & Callaway [Phys. Rev. B. (1977), 15, 298- 306] based upon a LCAO calculation with the KSG (Kohn & Sham and Gaspar) approximation for exchange [Kohn & Sham (1965). Phys. Rev. 140, A1133-1138; Gaspar (1954). Acta Phys. Acad. Sci. Hung. 3, 263-286]. The values obtained for f' as a function of energy are within about 0.2 electron units of those calculated from measured and tabulated absorption coefficients by Bonse & Hartmann-Lotsch [Nucl. Instrum. Methods (1984), 222, 185-188] and within about 0.5 electron units of their direct measurements by interferometric techniques in the range 30 to 3 eV below threshold. The variation of f' with scattering angle is negligibly small (less than 0.2 electron units on average). The present experiment demonstrates that powder techniques provide a simple and convenient method for the measurement of f' for many materials that are not available in forms suitable for the application of other techniques such as interferometry.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767385000897
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