Quantum molecular descriptors and adsorption properties of SCN- on (6,0), (7,0), (8,0), and Ga-doped (6,0) zigzag single-walled boron nitride nanotubes: a computational study

The behavior of the thiocyanate anion (SCN-) adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Ga-doped (6,0) zigzag single-walled boron nitride nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the SCN- interaction in selected sites of the nanotubes. Our results show that the pristine boron nitride nanotubes cannot significantly detect SCN-. The calculated binding energy of the Ga-doped (6,0) single-walled boron nitride nanotube indicated that SCN- can be absorbed significantly on the Ga site and these nanotubes can therefore be used for SCN- storage. Binding energy corresponding to adsorption of SCN- on the Ga site in the Ga-doped (6,0) single-walled boron nitride nanotube was calculated to be -263.3 kJ mol(-1). The calculated binding energies for SCN- in N-down orientation are higher than those in S-down orientation for all of the configurations. Also, we showed that the nanotube diameter has no significant role in determining the binding energy of SCN- and only the orientation and location of the SCN- and also doping of nanotubes by other atoms play an important role in determining the binding energy. The decrease in global hardness, energy gap, and ionization potential due to SCN- adsorption leads to a the lowering of stability and increase in reactivity of the (6,0) zigzag SCN-- and Ga-doped (6,0) zigzag SCN--boron nitride nanotube complexes.