ABSTRACT
This chapter summarizes a novel and stable crystal of silicon with hollow nanotubes penetrating through it. Its stability is testified with the calculations of the cohesive energy, geometry optimization, and phonon band structure. The structure and properties of nanotubular structure of the porous silicon (nt-p-Si) are calculated by density-functional theory (DFT) using the Cambridge sequential total energy package (CASTEP). The DFT calculation is known to have a systematic underestimation of the band gap. The chapter discusses the structure has remarkable properties, such as regular penetrating pores, direct band gap, wide frequency range optical activities, and anisotropy. The structure of nanotubes can store or transport small molecules or atoms, and the optical activities may be used in photo-chemical reactions. Therefore, nt-p-Si can serve as molecular sieves, electro-optical devices, new-style solar cells, photocatalysis, and aerospace materials. The nt-p-Si may be able to be used as a new semiconductor with similar properties to gallium arsenide (GaAs), without toxic elements.
