Understanding of powder diffraction patterns

Pattern component Crystal structure Specimen property Instrumental parameter 

Peak r Unit cell Absorption Radiation (wavelength) 

Peak r Atomic Preferred orientation Geometry and configuration 

In addition to the influence brought about by the instrumental parameters, there are two kinds of crystallographic (structural) parameters, which essentially define the structure of every powder diffraction pattern. These are the unit cell dimensions and the atomic structure (both the unit cell content and spatial distributions of atoms in the unit cell). Thus, a powder diffraction pattern can be constructed (or simulated) as follows  

Positions of Bragg peaks are established from the Braggs law as a function of the wavelength and the interplanar distances, i.e. (/-spacing. The latter can be easily calculated from the known unit cell dimensions (section 2.8). For instance, in the case of the orthorhombic crystal system permissible Bragg angles are found from 

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