model of closely packed atoms within crystalline solid.
the atoms, molecules or ions make solids may arranged in orderly repeating pattern, or irregularly. materials constituents arranged in regular pattern known crystals. in cases, regular ordering can continue unbroken on large scale, example diamonds, each diamond single crystal. solid objects large enough see , handle composed of single crystal, instead made of large number of single crystals, known crystallites, size can vary few nanometers several meters. such materials called polycrystalline. common metals, , many ceramics, polycrystalline.
in other materials, there no long-range order in position of atoms. these solids known amorphous solids; examples include polystyrene , glass.
whether solid crystalline or amorphous depends on material involved, , conditions in formed. solids formed slow cooling tend crystalline, while solids frozen rapidly more amorphous. likewise, specific crystal structure adopted crystalline solid depends on material involved , on how formed.
while many common objects, such ice cube or coin, chemically identical throughout, many other common materials comprise number of different substances packed together. example, typical rock aggregate of several different minerals , mineraloids, no specific chemical composition. wood natural organic material consisting of cellulose fibers embedded in matrix of organic lignin. in materials science, composites of more 1 constituent material can designed have desired properties.
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