diffractogram

A diffractogram is a graphical representation of how a material diffracts incident radiation, typically showing the intensity of the diffracted signal as a function of an angle, wavelength, or scattering vector. It is produced in diffraction experiments on crystalline or polycrystalline samples, such as X-ray diffraction (XRD), neutron diffraction, or electron diffraction. The resulting plot reveals peaks whose positions, shapes, and intensities carry information about the material’s crystal structure.

In X-ray and neutron diffraction, a common form of a diffractogram plots intensity versus the scattering angle 2θ. The peak positions are governed by Bragg’s law and relate to interplanar spacings within the crystal lattice. Peak widths provide insights into crystallite size and microstrain, while peak intensities reflect the arrangement and types of atoms in the unit cell. In powder diffractometry, the diffractogram is frequently used for phase identification and for estimating lattice parameters, crystallinity, and sample quality.

Data analysis often involves background subtraction, calibration, and peak fitting. Comparisons with reference patterns in databases enable phase identification, while quantitative analysis can estimate the proportions of phases in a mixture. Instrumental factors such as wavelength, detector geometry, and instrumental broadening must be considered, as they affect peak positions and shapes.

Diffractograms have broad applications in materials science, chemistry, geology, and physics, including characterizing crystal structure, assessing material quality, and monitoring phase transitions. Limitations include peak overlap in complex systems and sensitivity to sample preparation and preferred orientation.