We investigate the effects of the substitution of all the first series transition-metal (TM) atoms on the physical properties of (10,0) boron nitride nanotube (BNNT) using the DFT calculation. Three interesting results are as follows: First, the formation energies show a more stable system for the born (B) site substitution than nitrogen (N) site substitution. Second, reducing the bandgap of the TM-substituted BNNT with respect to the pristine BNNT can be mainly related to the presence of the new impurity states induced near the Fermi level by the d electrons of the TM atom, and a half-metal behavior has been obtained for Ti-, V-, Ni-, Co-, Cu-substitution at B-site and Fe-, V-, Ni-substitution at N-site. Third, besides the appearance of two up-and-down-spin channels, a new spin-crossover has been observed for Fe-, Ni-, Co-, Cu-substitution at B-site and Ti-, V-substitution at N-site which make them suitable to use in spintronic applications.
