Surface reaction of nitrogen with liquid group III metals

Surface reactions of atomic and molecular nitrogen (N-2) with liquid group III metals: Al, Ga, and In has been investigated by quantum mechanical calc ulations in density functional theory (DFT) formulation, using cluster repr esentation of metal surface. It has been shown that the N-2 molecule dissoc iates during adsorption on the surfaces of liquid group III metals. The N-2 dissociation energy barriers are equal to 3.0 eV, 3.4 eV, and 3.6 eV for A l, Ga, and In, respectively. They are much smaller that the dissociation en ergy of free N-2 molecule, equal to 9.76 eV. It has been also determined th at the adsorption of N-2 on surface of liquid Al is an exothermic and on Ga and In is an endothermic process. These results are consistent with experi mentally observed combustion of liquid Al in high pressure of nitrogen and the absence of combustion of both Ga and In. The process of dissolution of N atoms adsorbed on liquid Al surface has been also analyzed. The energy ba rriers for the direct jump of the N adatom from the surface position into t he liquid Al interior is equal to 1.3 eV. This suggests that the dissolutio n of N in liquid Al proceeds not by direct jumps of N adatoms into the liqu id interior but by Brownian motion of clusters consisting of these adatoms and neighboring Al atoms. The results of the calculations indicate that nit rogen solution in liquid group III metals consists of single N atoms strong ly attached to the surrounding Me atoms. (C) 2001 American Institute of Phy sics.