Ab Initio Study of Temperature, Humidity, and Covalent Functionalization-Induced Bandgap Change of Single-Walled Carbon Nanotubes

The effects of temperature, humidity, and covalent functionalization on the bandgap of single-walled carbon nanotubes (SWCNTs) are systematically investigated by ab initio calculations. The bandgap of SWCNTs has been found to decrease with the increase of temperature. Analysis of humidity effect indicates that water adsorption on the outer wall of SWCNTs widens the bandgap, but when the water molecules are adsorbed on the inner wall, SWCNTs with different radii and chiralities show different bandgap changes. We also show that covalent functionalization of SWCNTs leads to drastic deformation of the tube. Upon increasing the functional groups, the deformation is more obvious. It is worth noting that the tube deformation also greatly contributes to the change of the bandgap.