Quantum chemical study of fluorinated AlN nano-cage

Adsorption of 1, 2, 3, and 12 F atom(s) on the surface of Al12N12 nanocluster has been investigated using density functional theory. It has been found that the F atom strongly prefers to be adsorbed on Al site of the cluster rather than N one with the average Gibbs free energy change of −93.2 to 98.0 kcal/mol at 298 K and 1 atm. Average enthalpy change of the reaction is slightly increased by increasing the number of F atoms. The F adsorption considerably influences electronic properties of the cluster so that it is transferred from intrinsic semiconductor to p-type one. HOMO/LUMO energy gap of the cluster is narrowed and the Fermi level is dramatically shifted from −4.50 eV in the bare cluster to lower energies upon the F adsorptions along with increased work function of the cluster. This results in raised potential barrier of the electron emission for the cluster and hence hindering its field emission. Moreover, it has been shown that the following reaction may occur spontaneously at room temperature and 1 atm: Al12N12 + 6F2 → Al12N12F12.