Dependence of structural data from sin theta/lambda, extension in Rietveld refinement of virtually texture-free laboratory X-ray powder-diffraction data

摘要

The present work analyses the effects of reducing the resolution of a data set on the structural parameters of three compounds: nitratine NaNO3, gypsum CaSO4 center dot 2H(2)O, and K-alum KA1(SO4)(2) center dot 12H(2)O, characterized by an increasing degree of structural complexity. The unexpected result is that in the case of the near absence of preferred orientation, adequate structural information can be retrieved from data sets extending up to a minimum sine theta/lambda. value of ca. 0.4, corresponding to a 20 value of ca. 750 for CuK alpha radiation, at least for compounds of fairly moderate complexity (ca. 25 structural parameters). Therefore, in the case of experiments collected in step-scan mode, whenever time is a limiting factor, an increase of the peak/background ratio is more advantageous than the extension of the explored reciprocal lattice.