Mg-doped GaN nanostructures: Energetics, magnetism, and H₂ adsorption

Using density functional theory and generalized gradient approximation for exchange and correlation potential we show that Mg-doped GaN nanocages and nanotubes can be magnetic with Mg-contributed spins distributed over the neighboring N sites. Mg atoms show no tendency for clustering due to the positive charge residing on them; they can trap hydrogen in molecular form via the charge polarization mechanism. The binding energies of hydrogen lie in the range of 0.1-0.2 eV/ H2, which are ideal for storage applications under ambient thermodynamic conditions.