EXTRA: A program for extracting structure factor amplitudes from powder diffraction data.

Extraction of structure-factor amplitudes from a powder diffraction pattern is not a straightforward procedure. Peak overlapping and background estimation are the main obstacles to the process: they may introduce strong correlations among reflection intensities and heavy errors in their estimates. The program EXTRA is described, which, on the basis of the Le Bail algorithm, is able reliably to estimate the structure-factor amplitudes in a fully automatic way.