Shadowing and absorption corrections of high-pressure powder diffraction data: toward accurate electron-density determinations.

The shadowing of the primary beam and of reflections from a powder crystal sample enclosed in a diamond-anvil high-pressure cell (DAC) is described for unrestricted data-collection procedures. The corrections account for the shadowing of the data measured with point- or area-detector diffractometers and can be applied for any containers of environment devices enclosing a powdered sample. The general procedure for correcting the powder diffraction data can be applied for analysing and optimizing diffractometric procedures of data collection and provides facilities for collecting high-pressure powder diffraction data with the DAC positioned optimally and rotated to counteract the preferred-orientation and particle-size effects, and to increase the resolution of data. The quadrature effects of numerical integration for the accuracy of computed corrections have been analysed.