The electronic properties of chiral silicon nanotubes

This paper investigated the geometric structural and electronic properties of infinite chiral single- and doubel-walled silicon nanotubes (SWSiNTs and DWSiNTs) using density functional theory (DFT). With the periodic boundary conditions (PBC), the structures of infinite chiral silicon nanotubes (SiNTs) were obtained and their electronic properties were discussed in detail. The stability of the chiral SWSiNTs was enhanced with the increase of the diameter. For the chiral DWSiNTs, with the increase of the wall spacing, the stability of chiral DWSiNTs (n,n/2)@(2n,n) was gradually enhanced but the chiral DWSiNTs (2n,n)@(3n,3n/2) was reduced; and with the increase of the diameter, the stability of chiral DWSiNTs was gradually enhanced. And the chiral SWSiNTs (n,m) showed semiconductor properties when the chiral indexs were not multiple of 3; otherwise, they exhibited metal characteristics. The electronic properties of SWSiNTs (4,2) and (6,3) were abnormal due to the curvature effect. For chiral DWSiNTs, the orderliness of band gaps was the same as SWSiNTs. In other words, when the chiral indexs for two tubes were both multiple of 3, they show metal characteristics. When the chiral indexs of just one tube were not multiple of 3, they exhibited semiconductors properties, except for (4,2)@(8,4) which showed metal characteristics due to the curvature effect.