Zig-zag boron nitride nanotubes functionalization with acetylene molecules: a density functional theory study

Spin-polarized first-principles total-energy calculations have been performed in order to investigate the organic functionalization of zig-zag boron nitride nanotubes (BNNTs) with acetylene molecules. Calculations have been done within the periodic density functional theory (DFT), including van der Waals interactions. We have considered zig-zag (n, 0) BNNTs with n=5, 10 and 15. Nanotubes with no defects exhibit weak interactions with the acetylene molecules. Therefore, we have generated boron and nitrogen vacancy-type defects to favor the adsorption. Results show that chemisorption occurs in all cases with adsorption energies in the range of -3.6eV to -5.3eV, with adsorption in nanotube (5, 0) and (10, 0) being the most and least favorable, respectively. We find that nanotubes with boron vacancies show a stronger interaction than the nanotubes with nitrogen vacancies. Minimum energy pathways show that activation energies are of the order of 0.1-1.6eV, with the lowest energy barrier for the nanotubes with nitrogen vacancies. Analysis of the density of states (DOS) show that the organic molecule modifies the electronic structure.