A common theory of line broadening and rocking curves

X‐ray diffraction peak broadening is discussed in terms of line broadening and rocking‐curve broadening in a novel theoretical description. The nonlocal strain tensor is factorized by using the method of polar decomposition instead of the more conventional separation into symmetrical and antisymmetrical components. A number of X‐ray line‐broadening and rocking‐curve experiments on the same single crystals or individual grains in bulk polycrystals prove that plastic deformation produces strained subgrains mutually rotated by rigid‐body rotations. The novel theoretical description appropriately accounts for the rigid‐body rotation and strain at the same time and provides straightforward separation of the two effects of line and rocking‐curve broadening in the radial and normal directions of the diffraction vector. The mathematical results are discussed in terms of experiments of X‐ray diffraction, Laue asterism and electron backscatter diffraction. From the experimental results it is shown that the simultaneous evaluation of line and rocking‐curve broadening provides qualitative information about the redundant and geometrically necessary character of dislocations, not available if only one or the other is accessible.