6. Identification of phases

The most important application of PXRD is undoubtedly the identification of the phases present in a sample. The positions of the peaks depend on the shape and dimensions of the unit cell, and the intensities of the peaks depend on the arrangement of atoms in the crystal. Consequently, each phase can be identified by its characteristic pattern. With very rare exceptions, two distinct phases have different diffractograms. A polyphase material exhibits a diffractogram that is the superposition of each of the diffractograms of the phases comprising it; the intensities are proportional to the amount of each phase.