A new phase of carbon

An unknown structure with close to six-fold symmetry in diffraction patterns has been found by TEM-studies of C-60- and C-70-samples after different stages of thermobaric treatment. The new phase may be considered as intermediate between graphite and diamond. The value 0.51 nm of parameter a, of this phase was found to be closed to twice the value for graphite and to twice the value of parameter d(110) in diamond. The atoms situated in the nodes of (0001)-graphite planes with doubled a(o)-parameter take part in the connection of (0001)-planes by sp-3 bonds. The connection of (0001)-graphite planes results in splitting of these planes between the layers. Four layers form the unit cell of the new phase. The unit cell contains 24 atoms. This crystal lattice can be represented as a triclinic one with parameters: a=b=0.51 nm, c=0.745 nm, alpha=beta=82 degrees, gamma=120 degrees. The density of the new phase lies in the range of carbyne densities. (C) 1999 Elsevier Science Ltd. All rights reserved.