Naslov
Truncation and background level errors in diffraction profile analysis

Autori
Skoko, Željko ; Popović, Stanko ; Štefanić, Goran

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
The twentieth Croatian-Slovenian crystallographic meetin - CSCM20. Book of abstracts programme. / - , 2011, 52-52

Skup
The twentieth Croatian-Slovenian crystallographic meetin - CSCM20.

Mjesto i datum
Baška, Hrvatska, 15.07.2011. - 19.07.2011

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
truncation; diffraction line profile; level error

Sažetak
The profile truncation error and the background level error are inherent in diffraction line profile analysis and in structure refinement in general. This combined error has been calculated for several bell-shaped functions usually used in the analysis of diffraction pattern. The functions have been truncated at points where they fall to one hundredth of their maximum ; this choice has been arbitrary and corresponds to an average detection limit in intensity measurement. It has been shown that, in line with qualitative facts known in literature, the error more affects the functions which are usually used to describe the crystallite size parameter than the ones used to describe the strain parameter. The error is the biggest for the Cauchy function (12.7 %), the smallest for the Gauss function (2.7 %), while the errors for the Voigt and pseudo-Voigt functions are in between of those for the Cauchy and Gauss functions (for instance, the error is 8.6 % if the FWHM's are equal for the Gauss and Cauchy components). The steps and precautions, which are necessary in order to minimize the error, have been suggested through simple examples. The values of the crystallite size and strain parameters, obtained from integral breadths derived by the Stokes deconvolution, have been compared with those which have followed from the Warren-Averbach treatment of broadening S. Popović, Ž. Skoko and G. Štefanić, Z. Krist. (2011), accepted for publication . In order to find out the dependence of the integral breadth on the background level error for pure diffraction profile obtained by the Stokes deconvolution, the background level has been intentionally overestimated up to 5 %, in steps of 0.1 to 0.5 %. As expected, both the integral intensity of the profile (that is, the surface under the profile) and the intensity maximum of the profile have decreased with the progressive overestimation of the background level. But, the decrease of the integral intensity has been found bigger than the decrease of the maximum intensity. Therefore, the integral breadth has decreased (for 3%) with the overestimation of the background level (for 5%). That dependence has been fitted by a third order polynomial function. The extrapolation of that dependence to the point of zero background level overestimation may yield a true background level of diffraction profile ; this procedure thus eliminates a possible initial error in the background level.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

POVEZANOST RADA