Ordered Amorphous Carbon Clusters

By squeezing the daylights out of solvated C₆₀ fullerenes, materials scientists have created a hybrid material that maintains a long-range ordered lattice structure like that of a crystal even though its fundamental building blocks are amorphous carbon clusters (Science, DOI: 10.1126/science.1220522). Atomic structure is typically based on short-range order for liquids and amorphous solids or long-range repeating patterns for crystalline materials—but not both at the same time. A research team led by Lin Wang of the Carnegie Institution of Washington compressed C₆₀ fullerene molecules solvated with xylene molecules in a diamond anvil cell. Using a combination of X-ray and other spectroscopic techniques, in conjunction with large-scale computer simulations carried out by Xiao Cheng Zeng’s group at the University of Nebraska, Lincoln, the researchers found that when the pressure reaches 32 gigapascal, or about 316,000 atm, the fullerene spheres collapse to form amorphous clusters separated by xylene molecules. The xylene molecules hold steady, keeping the carbon clusters aligned to maintain long-range crystalline order. Like other forms of carbon, the new material is anticipated to exhibit a range of mechanical and electronic properties, depending on the ratio of fullerene molecules to solvent molecules, the type of solvent used, and the addition of metal atom dopants.