ABSTRACT
Among solid materials there are several categories, including crystalline, amorphous and nanostructured solids. Amorphous solids are completely lacking in the translational symmetries that characterize crystals, but do have short-range order arising from the fact that the material consists of atoms that are tightly bound to each other and that have definite spatial size, characterized by angstroms (1010 m). Thus one atom is more likely to have nearest-neighbor atoms at a distance of approximately one atomic diameter, rather than at slightly more or less distance. Nanostructured solids consist of tightly bound crystallites, within each of which translational crystalline order is qualitatively evident, but limited to nanometer (109 m) size. Paradoxically, the mismatch of different crystallite orientations at their mutual boundaries produces a higher level of disorder than occurs in amorphous solids. The situation is clearly illustrated and discussed by Birringer (1989).
