The use of X-rays to study the structure of crystals mainly through the X-ray diffraction phenomenon in the crystal. The diffraction phenomenon of X-ray in crystal is essentially the result of the interference between the atoms and the X-ray when the X-ray is irradiated to the object. Each type of crystal produces its own characteristic diffraction pattern, which reflects the distribution of atoms inside the crystal. We can analyze various problems of the internal structure of the crystal through the diffraction phenomenon, so as to determine the type of the substance, as well as the content of the substance.

Laue equation is a set of equations derived from the geometrical principles of diffraction and the characteristics of periodic arrangement of crystals in three-dimensional space.

As can be seen from the figure, when the X-ray is projected on the three-dimensional crystal in the direction of S0, the three diffraction rings have the only common intersection point, and the diffraction direction is from the origin to the direction S indicated by the intersection point. Therefore, the diffraction signal can be obtained at a specific Angle after the detector is rotated, which can be reflected in the characteristic diffraction spectrum.

Bragg's law

A crystal is considered to be made up of atomic planes, each of which emits scattered light in all directions at the same wavelength as the incident light.

1. Not all crystal faces can produce diffraction. It is possible for a crystal face to produce multiple stages of diffraction.

2. When the wavelength is constant, the diffraction Angle is only related to the size of the cell, and is independent of the specific composition of the crystal.