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A semi-empirical asymmetry function for X-ray diffraction peak profiles

Published online by Cambridge University Press:  10 January 2013

P. Riello
Affiliation:
Dipartimento di Chimica Fisica, Università di Venezia, DD 2137, 30123 Venezia, Italy
P. Canton
Affiliation:
Dipartimento di Chimica Fisica, Università di Venezia, DD 2137, 30123 Venezia, Italy
G. Fagherazzi*
Affiliation:
Dipartimento di Chimica Fisica, Università di Venezia, DD 2137, 30123 Venezia, Italy
*Corresponding
a)To whom correspondence should be addressed.

Abstract

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

Type
Research Article
Copyright
Copyright © Cambridge University Press 1995

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References

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