A new phase of carbon

An unknown structure with close to six-fold symmetry in diffraction pattern s has been found by TEM-studies of C-60- and C-70-samples after different s tages of thermobaric treatment. The new phase may be considered as intermed iate between graphite and diamond. The value 0.51 nm of parameter a, of thi s 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 conn ection of (0001)-planes by sp-3 bonds. The connection of (0001)-graphite pl anes results in splitting of these planes between the layers. Four layers f orm the unit cell of the new phase. The unit cell contains 24 atoms. This c rystal 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 o f the new phase lies in the range of carbyne densities. (C) 1999 Elsevier S cience Ltd. All rights reserved.