Dependence of structural data from sinθ/λ extension in Rietveld refinement of virtually texture-free laboratory X-ray powder-diffraction data

The present work analyses the effects of reducing the resolution of a data set on the structural parameters of three compounds: nitratine NaNO3, gypsum CaSO4·2H2O, and K-alum KAl(SO 4)2·12H2O, 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 sinθ/λ value of ca. 0.4, corresponding to a 2θ value of ca. 75° for CuKα 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.