The X-ray diffraction pattern serves as the most reliable foundation for determining polycrystalline patterns, and the X-ray diffraction pattern is frequently regarded as the "fingerprint" of crystalline patterns. 

The X-ray diffraction data obtained after the test of powder X-ray diffractometer are classified into the following three categories: (1) The determination of the polycrystalline type by the 2θ angle and crystal plane spacing (d value) represents the arrangement and positional information of atoms and molecules in the drug API; it is the characteristic information of the crystal type. (2) Peak height, peak strength and relative peak strength are the statistics of the distribution of different crystal planes in the crystal pattern, which is the characteristic information of the sample crystal pattern and the basis for quantitative analysis of the crystal pattern. (3) FWHM indicates the peak shape of the diffraction peak, reflecting the properties of the polycrystal grain size and shape, and does not serve as the characteristic information of the crystal type.