ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
Convolution products Were obtained by folding a specimen-related function into another function representing the intrinsic profile of the diffractometer used in this study. The instrumental contributions were modeled with three split-Pearson VII functions: one for each of the α1, α2 and α3 components in the Cu Kα spectral distribution. The positions and intensities of the α2 and α3 lines were based on those of the α1 line while their shapes were constrained to follow that of the α1. Values of the variable parameters of these functions, obtained from a `defect-free' specimen, were fit with polynomials to establish four discrete curves from which the instrument profiles could be synthesized at any diffraction angle. Both a normalized Lorentzian and a Gaussian function were evaluated for use in representing the specimen contributions. The integral breadth (β) of the specimen function was adjusted until the instrument-specimen convolution product best matched the observed profile. In specimens with small crystallite size, the angular dependence of β for the specimen profile followed the Scherrer relation while, in a strained specimen, the angular dependence followed the simple 4ε tan θ relation. In both cases, the specimen contributions were best modeled by a Lorentzian-type function.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889888014487
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