Stability of hollow spheroidal silicon clusters Si-n and SinHn

The structures of Si-n and SinHn fullerenes with 20 less than or equal to n less than or equal to 60 are calculated in the MINDO/3 approximation using the Monte Carlo technique for geometry optimization. The calculations show that spheroidal silicon clusters consisting of more than 36 atoms are stab le and the bond energy increases with their size. This increase is not noti ced for compact clusters calculated as an alterntative. For n greater than or equal to 40-50 the latter have lower bond energies compared to fullerene s. The geometry optimization of the tetrahedral cluster Si-45 results in a structure close to spheroidal, which gains in bond energy. The addition of hydrogen atoms to small deformed fullerenes and their geometry optimization make it possible to obtain stable spheroidal structures SinHn whose bond e nergy is greater than that of alternative compact silicon hydride clusters. When the size of spheroidal clusters SinHn increases, i. e., when n > 36, the hydrogen elimination barriers decrease abruptly; the SinHn diamond stru cture of the cluster is more advantageous when n greater than or equal to 5 0.