Graphite was used for years in lubricants, pencils, and batteries before researchers tried to separate it into graphene, a one-atom-thick layer of carbon atoms with enormous potential in electronics. In hindsight, could there be other solids like graphite that have simply been missed? To help identify them, Sébastien Lebègue, of the French National Center for Scientific Research (CNRS) in Nancy, and his colleagues have mined a vast database of crystal structures and pinpointed they believe can be easily exfoliated into atomically-thin layers. As reported in Physical Review X, several of these materials could have technological applications.
Graphite peels easily because its atoms are strongly bonded in one plane but weakly bonded between these planes. Lebègue et al. identified common geometrical traits of such materials, including a large separation between planes of atoms and an atomic packing density that is neither too high (as in metals) nor too low (as in molecular solids). They used these traits to design a search algorithm that sifted through thousands of solids in the Inorganic Crystal Structure Database, looking for a match.
The search turned up familiar materials including graphite (thankfully), its structural cousin hexagonal boron nitride, and a family of materials called the transition-metal dichalcogenides. The real potential lies in those tagged compounds with strongly bonded 2D sheets whose properties haven’t yet been studied in depth. According to the authors’ calculations, several of these materials have 2D layers that are semiconducting with a moderately sized band gap, a property essential for making transistors and one that even graphite lacks. – Jessica Thomas
Correction (9 July 2013): The Synopsis incorrectly stated that the materials FeSe and LiFeAs were dichalcogenides. This has been corrected.