Electronic and magnetic properties of 5d atoms doped aluminium nitride nanotubes: a first-principles calculation

A first-principles calculation based on density functional theory is carried out to reveal the geometry, electronic structure and magnetic properties of aluminium nitride nanotubes (AlNNTs), whose Al/N atoms are substituted by 5d atoms (Al_5d or N_5d). The pure-AlNNTs and AlNNTs with Al vacancy (V_Al) and N vacancy (V_N) are also investigated for comparison. Results show that the local symmetry of Al_5d system is similar to C_3v, while the N_5d system exhibits a large geometric deviation from C_3v. When AlNNTs are doped by the same 5d atom, the bonding energy of Al_5d is higher than that of N_5d; when 5d atoms substitute for Al/N atoms, the bonding energy of system decreases along with the atomic number growth. There exist obvious impurity energy levels in the band gap, and the density of states (DOSs) are presented. The total magnetic moment differs from each other when doped by different atoms, and the total magnetic moments of doped systems present a strong regularity. The impurity energy levels and total magnetic moments are explained by the molecular orbital theory under C_3v local symmetry. (authors)