Ab-initio calculations using density functional theory (DFT) are used to investigate the non-covalent interactions between single wall armchair boron nitride nanotubes (BNNTs) with open ends and several heterocyclic molecules: thiophene (T; C4H4S), benzothiophene (BT; C8H6S) and dibenzothiophene (DBT; C12H8S). In the armchair model the nanotubes exhibit (n, n) chirality; here we consider n = 5. The exchange-correlation energies are treated according to the Hamprecht-Cohen-Tozer-Handy functional in the generalized gradient approximation (HCTH-GGA). A base function with double polarization is used. The geometry optimization of (5,5) BNNT-X; X = T, BT and DBT has been carried out using the minimum energy criterion in 5 different configurations of the molecules adsorbed on the nanotube. Our computer simulations have found that the preferential adsorption site of the molecule on the nanotube surface is the parallel configuration for BT and DBT, and at one nanotube end for the T fragment, with all cases having physical interactions. The polarity exhibits an increase which favors the possible dispersion, provided the electrons are polarized. The nanostructure functionalization increases the chemical reactivity which in turn enhances interactions between the molecule and the nanotube. The BNNT-dibenzothiophene work function reduction as compared with the pristine case yields the improvement of the field emission properties.
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