A COMPARATIVE-STUDY OF C-60, SI-60, AND GE-60

Relative stabilities of the fullerenic structures C-60, Si-60, and Ge- 60 are studied by means of semiempirical quantum-chemical methods. It is suggested that atomization energies rather than heats of formation should be used for the purpose at this level of description. In the fo rmer terms Siso and Ge-60 are located higher than the fullerene itself by about 4100 and 6500 kcal/mol, respectively. A poor SCF convergence is reported for both fullerene analogues. While Si-60 still exhibits the exact Ih symmetry, the Ge-60 cage shows some distortion from the h ighly symmetric form though the fullerenic topology is present. Mass e ffects create a considerably narrow vibrational spectrum for Siso and especially Ge-60. A related computation on B-60 suggests a better ener gy position comparing to Si-60.