Magnesium boride nanotubes: Relative stability and atomic and electronic structure

A comparative study of the energies and the electronic structure of MgB_x nanotubes is performed within the framework of the density functional theory. Different basic compositions (x) 2 for diboride and x) 3 for triboride) and different diameters (3 A° < D < 18 A°), as well the exterior, interior, and staggered placement of magnesium atoms, are considered. Energy analysis reveals a nontrivial bending behavior of the MgB2 sheets, such that the tubes with exterior and staggered configurations display the energy minima at certain small diameters (of the boron cage sublattice). The semiconducting behavior of narrow MgB₂ nanotubes with exterior Mg position was observed.