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Onion-like graphitic particles 167
like particle: spherical or polyhedral) and the size 5. S. Iijima, J. Crysf. Growth 50, 675 (1980).
where the transition is between these closed surface 6. D. Ugarte, Chem. Phys. Lett. 198, 596 (1992).
particles and the macroscopic planar graphite. There 7. Y. Saito, T. Yoshikawa, M. Inagaki, M. Tomita, and T.
Hayashi, Chem. Phys. Lett. 204, 277 (1993).
are still several difficulties in answering this question: 8. R. S. Ruoff, D. C. Lorents, B. Chan, R. Malhotra, and
(a) from the theoretical point of view, the large number S. Subramoney, Science 259, 346 (1993).
of atoms to be considered renders the computational 9. M. Tomita, Y. Saito, and T. Hayashi, Jpn. J. &pi.
evaluation very difficult; (b) from the experimental Phys. 32, L280 (1993).
point of view, the quasi-spherical structures have only 10. D. Ugarte, Chem. Phys. Lett. 209, 99 (1993).
11. D. Ugarte, Nature 359, 707 (1992).
been synthesised in situ in an electron microscope. 12. T. W. Ebbesen, P. M. Ajayan, H. Hiura, and K. Tani-
At present, major efforts are being done to de- gaki, Nature 367, 519 (1994).
velop the production and purification of macroscopic 13. W. A. de Heer and D. Ugarte, Chem. Phys. Lett. 207,
quantities of the quasi-spherical onion-like particles. 480 (1993).
The understanding of the formation mechanism and 14. D. Ugarte, Carbon 32, 1245 (1994).
15. D. Ugarte, Europhys. Lett. 22, 45 (1993).
energetics involved would allow the development of 16. K. Yamada, H. Kunishige, and A. B. Sawaoka, Natur-
efficient production methods. The annealing on wissenschoften 78, 450 (1991).
nanometer-sized diamonds reported by Kuznetsov 17. N. Hatta and K. Murata, Chem. Phys. Lett. 217, 398
(1994).
et al. [ 191 presents a promising way to generate compact 18. L. S. Weathers and W. A. Basset, Phys. Chem. Miner-
graphitic particles, if we are able to overcome the dif- als 15, 105 (1987).
ficulty of producing large quantities of nanodiamonds. 19. V. L. Kuznetsov, A. L. Chuvilin, Y. V. Butenko, I. Y.
We hope that macroscopic samples of quasi-spherical Mal'kov, and V. M. Titov, Chem. Phys. Lett. 222, 343
onion-like particles will soon become available, and ( 1994).
then we will be able to characterize these systems in 20. R. E. Smalley, Acc. Chem. Res. 25, 98 (1992).
21. A. Oberlin, Carbon 22, 521 (1984).
detail. Probably a new generation of carbon materi- 22. R. E. Smalley, Mater. Sci. Eng. B 19, 1 (1992).
als can be generated by the three-dimensional pack- 23. Q. L. Zhang, S. C. O'Brien J. R. Heath, Y. Liu, R. E
ing of quasi-spherical multi-shell fullerenes. Curl, H. W. Kroto, and R. E. Smalley, J. Phys. Chem.
90, 525 (1986).
24. H. W. Kroto and K. McKay, Nature 331, 328 (1988).
Acknowledgements-The author is most grateful to W. de 25. D. Ugarte, Chem. Phys. Left. 207, 473 (1993).
Heer for invaluable discussions and advice. We are indebted 26. A. Maiti, C. J. Bravbec, and J. Bernholc, Phys. Rev.
to R. Monot and A. Chatelain for several useful remarks. Lett. 70, 3023 (1993).
We thank the Brazilian National Council of Science and 27. D. Tomanek, W. Zhong, and E. Krastev, Phys. Rev. B
Technology (CNPq) and Swiss National Science Foundation 48, 15461 (1993).
for financial support. 28. H. W. Kroto, Nature 359, 670 (1992).
29. K. G. McKay, H. W. Kroto, and D. J. Wales, J. Chem.
SOC. Faraday Trans. 88, 2815 (1992).
REFERENCE§ 30. M. Yoshida and E. Osawa, Ful. Sci. Tech. 1, 55 (1993).
3 1. D. York, J. P. Lu, and W. Yang, Phys. Rev. B 49,8526
1. H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl, and (1 994).
R. E. Smalley, Nature 318, 162 (1985). 32. L. T. Scott, M. M. Hashemi, and M. S. Bratcher, J. Am.
2. W. Kratschmer, L. D. Lamb, K. Foristopoulos, and D. R. Chem. SOC. 114, 1920 (1992).
Huffman, Nature 347, 354 (1990). 33. A. Maiti, C. J. Brabec, and J. Bernholc, Modern Phys.
3. S. Iijima, Nafure 354, 56 (1991). Rev. Lett. B 7, 1883 (1993).
4. T. W. Ebbesen and P. M. Ajayan, Nature 358, 220 34. J.-C. Charlier and J.-P. Michenaud, Phys. Rev. Lett. 70,
(1992). 1858 (1993).