Competitive diamond-like and endohedral fullerene structures of Si70.

We performed first-principles calculations to study the structure and stability of Si(70) cluster. The results from the density functional theory calculation with the Becke-Lee-Yang-Parr and B3LYP exchange-correlation functionals suggest that a diamond-like Si(70) isomer is the most stable structure, in contrast to endohedral fullerenes of Si(70). On the other hand, an endohedral fullerene of Si(16)@Si(54) was found to be slightly lower in energy than the diamond-like Si(70) if the Predew-Burke-Ernzerhof functional is used. Our calculation results suggest that around n = 70, the endohedral fullerene and diamond-like isomer are expected to be competitive. The calculated IR vibration spectra, ionization potential, and inverse mobilities were also calculated and discussed.