ABSTRACT
X-ray diffraction is mainly used for investigations of crystal structures. The fundamental geometry and structure of crystals are introduced, explaining how the atoms are arranged in the crystals and how crystals diffract x-rays. The lengths and angles are the lattice parameters of the unit cell. Based on the symmetries and shapes of unit cells, all crystals are classified into several crystal systems. The relations between the interplanar spacing, plane index, and lattice parameters were introduced for various crystal systems. Database querying of diffraction angles and thus interplanar spacing of strong peaks in an x-ray diffractometry spectrum, is a more convenient way to determine the crystal structure. X-rays are short-wavelength electromagnetic radiation, with diffraction x-rays in the 0. 01–2. 5 nm range. When x-rays encounter a solid sample, they are partially transmitted and partially absorbed. The scattering of x-rays can be categorized as coherent scattering and incoherent scattering.
