Hydrostatic-pressure-induced porous gallium nitride from nanotube bundles: an ab initio study

Ab initio calculations show that (5,5) and (6,6) single-walled gallium nitride nanotubes (GaN NTs) in bundles could aggregate spontaneously to form new condensed phases when bundled tubes are close enough under hydrostatic pressure. The new GaN phases have typical porous structures, constructed by alternating tetragons and hexagons around the original tube walls. Owing to the different compatibilities of the chirality of the tube with the symmetry of the array, the new phase formed from (5,5) GaN NT bundles is triclinic and that from (6,6) ones is hexagonal. These porous GaN phases possess tetrahedral bonding corresponding to sp(3) hybridization, different from sp(2) hybridized bonding in individual GaN NTs. The interaction between tubes not only controls the structural transformation but also influences the electronic structure of porous GaN. We expect that the two-dimensional-channeled porous structure of GaN is advantageous for the usage of GaN as the molecular sieve and as the excellent dilute magnetic semiconductor by considerable magnetic doping.