Materials Science
Many layered solids intercalate guest molecules. A famous example is the intercalation of potassium into graphite. Intercalation expands the "van der Waals gap" between sheets, which requires energy. Usually this energy is supplied by charge transfer between the guest and the host solid, i.e., redox. Aside from graphite, well-known intercalation hosts are the layered dichalcogenides such as tantalum disulfide and iron oxychloride. In characteristic manner, intercalation is analyzed by X-ray diffraction, since the spacing between sheets increases, and by electrical conductivity, since charge transfer alters the number of charge carriers.
Read more about this topic: Intercalation (chemistry)
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