Between Graphite and Diamond

Pure carbon has a wide variety of atomic structures, such as diamond and graphite, but the structure created by a 2003 graphite compression experiment has been controversial. Now two teams of theorists have followed different lines of evidence to suggest that the structure involves a 3D network of four-atom rings called bct-carbon. In the 26 March Physical Review Letters, one team reported simulations that agree with the 2003 data, and in the November Physical Review B, the other team shows that the energy barrier to create bct-carbon is low enough that it could have appeared in the 2003 experiment. Researchers say the results point to the existence of a new and unexpectedly simple form of carbon.