LAUSR

Abstract In this article, we aim to use LGTO-PBC-DFT calculation method with PBEPBE/6–31G(d) basis sets and PBC model to optimize geometric structure, obtain electron characteristics and band gaps of (n, m) chiral (6 ≤ n ≤ 16, 2 ≤ m ≤ 8); (n, 0) zigzag (3 ≤ n ≤ 15) and (n, n) armchair (2 ≤ n ≤ 8) pure infinite length single-walled Silicon nanotubes. We have obtained that the HOCO-LUCO gaps decrease with the radii of the SWSiNTs increase by using the PBEPBE functional and 6–31G(d) basis set. Most of the infinite length SWSiNTs which we studied are narrow band gaps semiconductors. Perhaps the surface structure is the most important factor affecting the band gap of the nanotubes. There have been a research on the infinite silicon nanotubes and with the increase of the tube radius, an indirectdirect band gap transition has been revealed. For all the armchair SWSiNTs, the infinite zigzag SiNTs (n,0), (3 ≤ n ≤ 9) and the infinite chiral SWSiNTs (6, 2), (9, 3), (10, 5), (12, 6) are semiconductors with indirect band gaps. While for the infinite zigzag SiNTs (n, 0) 15 ≥ n ≥ 10, and the infinite chiral SWSiNT (12, 4) are semiconductors with direct gaps at Ｘ point, the direct gaps open at Ｘ point. It is possible that direct band gap will become potential building blocks for electronic and optoelectronic devices.