A Comparative Study of C60, Si60, and Ge60

Relative stabilities of the fullerenic structures C60, Si60, and Ge60 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 former terms Si60 and Ge60 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 Si60 still exhibits the exact Ih symmetry, the Ge60 cage shows some distortion from the highly symmetric form though the fullerenic topology is present. Mass effects create a considerably narrow vibrational spectrum for Si60 and especially Ge60. A related computation on B60 suggests a better energy position comparing to Si60.