Before you move on to multigrain indexing, you will need to know:

• what phases you are looking for,
• their crystal structures and cell parameters.

If you have a decent powder diffraction pattern to work with, you can try to do so with typical software people use in DAC experiments: dioptas, maud, etc.

There is a second option:

• collect diffraction peaks using peak-search,
• generate a 2-theta histogram of peaks.

This will be discussed below.

Generating a 2-theta histogram of peaks identified with a peak search has several advantages:

• most of the background signal (diamonds, shadows, etc) has been removed,
• a strong powder signal from the pressure medium will be partly removed,
• the signal from the sample you are trying to index is stronger,
• the histogram is based on the peak center of mass only, and hence removes the broadening due to grain size or internal strains.

Some drawbacks

• this is not a true powder diffraction pattern, peak broadening, in particular, is different,
• current easy-to-use versions do not sum intensities, but count the number of peaks for a given 2theta. The recovered intensity is proportional to the multiplicity, and not the structure factor. Diffraction intensities are messed up an can be used for structural refinements.