Density functional theory study of structure and bonding of water on alumina nanotube

Geometry and electronic structure of alumina nanotubes (ANT) were studied using hybrid B3LYP density functional method. Three models of finite length nanotubes, including nanotube with closed ends (CEANT), nanotube with one opened end (OOEANT) and nanotube with two opened ends (TOEANT) were considered. The calculated density of states and natural atomic orbitals analysis predict that HOMO and LUMO of nanotubes arise mostly from O 2p and Al 3s atomic orbitals, respectively. For CEANT and OOEANT, the electron density of HOMO concentrates over the center of nanotube, while the LUMO distributes over the end caps. HOMO and LUMO of TOEANT localize at the center of nanotube. The adsorption strength of the active sites of alumina nanotube (OOEANT) was evaluated using the interaction with water molecule. The relative strength of alumina nanotube adsorption sites was predicted as opened end > closed end (end cap) > hemisphere cap > center of nanotube using CAM-B3LYP method.