Theoretical studies on the electronic structures and spectra of single silicon-doped SWCNTs

摘要

The equilibrium geometries and electronic structures of a series of SWCNTs doped with a silicon atom were studied by using density function theory (DFT). The most stable doping site of silicon predicted at B3LYP/6-31G(d,p) level was located near the boundary of the SWCNTs. The energy gaps of (3,3) C_(48), (3,3) C_(60) and (3,3) C_(72) were respectively decreased by 0.43, 0.25 and 0.14 eV after doping. Based on the B3LYP/6-31G(d) optimized geometries, the electronic spectra of the doped SWCNTs were computed using the INDO/CIS method. The first UV absorption at 973.9 nm of (5,5)-Si(L) (C_(59)Si) compared with that at 937.5 nm of (5,5) (C_(60)) was red-shifted. The ~(13)C NMR spectra and nuclear independent chemical shifts (NICS) of the doped SWCNTs were investigated at B3LYP/6-31G(d) level. The chemical shift at 119.4 of the carbon atom bonded with the silicon atom in (3,3)-Si(L) (C_(59)Si) in comparison with that at 144.1 of the same carbon atom in (3,3) (C_(60)) moved upfield. The tendency of the aromaticity (NICS = -0.1) for (3,3)-Si(H) (C_(47)Si) with respect to that of the anti-aromaticity (NICS = 6.0) for (3,3) (C_(48)) was predicted.