A theoretical study of the geometries, and electronic and surface properties of sphere-like (SiB)2n (n = 6-27, 30) functional nanomaterials.

The geometries and electronic properties of (SiB)2n (n = 6-27, 30) clusters are systematically investigated based on the gradient corrected Perdew-Burke-Ernzerhof exchange-correlation functional. In particular, the (SiB)36 cage is identified as the most stable nanocluster and (SiB)2n (n = 6-27, 30) nanocages prefer to have sphere-like geometries. By increasing the (SiB)2n (n = 6-27, 30) nanocage size, the calculated energy gaps of (SiB)2n (n = 6-27, 30) nanocages generally decrease and absorption wavelengths of the spectra of (SiB)2n (n = 6-27, 30) nanoclusters are elongated. The varied size of the nanoclusters leads to a quantum confinement effect indirectly. Interestingly, the nanosized (SiB)30-60 cages exhibit a stronger capacity for solar energy absorption or conversion due to both narrow HOMO-LUMO energy gaps and a large DOS near LUMO and HOMO levels. Finally, electronic charges transferred from silicon atoms to their surrounding boron atoms in (SiB)2n (n = 6-27, 30) contribute to the metallic characteristic and B-Si ionic bonds, and eventually enhance the stabilities of the nanocages.