The transformation of polyhedral particles into graphitic onions

We propose that the carbon particle structures which are transformed by ejection of pentagonal and neighbouring carborn rings, under high electron irradiation, are flexible and carl be moulded via energy minimization into quasi-spherical arrangements. In our model, additional pentagonal and heptagonal rings are required to generate the stable quasi-spherical onion-like structures, which can be sym metric (crystalline) or nonsymmetric (amorphous). The possibility to generate higher genus fullerene-like structures by introducing additional heptagonal rings on the outer shell of the quasi-spherical onion is also discussed. (C) 1997 Elsevier Science Ltd.