New phases of C60 synthesized at high pressure

• Published in: Science (American Association for the Advancement of Science) 1994-06, Vol.264 (5165), p.1570-1572
• Main Authors: IWASA, Y, ARIMA, T, TYCKO, R, DABBAGH, G, KRAJEWSKI, J. J, THOMAS, G. A, YAGI, T, FLEMING, R. M, SIEGRIST, T, ZHOU, O, HADDON, R. C, ROTHBERG, L. J, LYONS, K. B, CARTER, H. L, HEBARD, A. F
• Format: Article
• Language: English
• Subjects: Carbon; Carbon allotropes; Chemistry; Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...); Exact sciences and technology; Inorganic chemistry and origins of life; Preparations and properties
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.264.5165.1570

The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked.