The projected density of states is presented for the pristine BNNT (Fig. 3(a)) and CrO3adsorbed on BN nanotube (Fig. 3(b)) in the most stable configuration. When the CrO3molecule is adsorbed on the BNNT surface, the PDOS alters, and localized levels are introduced at the valence and at the conduction bands. As we can see in Fig. 3(b),there is a strong hybridization in region −10.0 eV and −6.5 eV in valence band, and −1.8 eV and −0.8 eV in conduction band. The hybridization between the Cr, O, B and N orbitals suggests a covalent interaction between the CrO3molecule and the BNNT. Also, it is possible to see that the valence and the conduction states are delocalized and new levels appeared in the gap region with the contribution of the Cr and O atoms. The modifications that occur are probably due to strong redistribution of charge between BN nanotube and CrO3molecule. The energy gap 4.32 eV and 2.53 eVin pristine BNNT and BNNT interacts with CrO3molecule, respectively. The other change in the PDOS is a Fermi level shift of 1.18 eV to valence band in comparison with pristine BN nanotube.