First-principles study of the geometrical and electronic structures of In _nN _2 (n=1-10) clusters

摘要

The structures and electronic properties of In _nN _2 (n=1-10) clusters have been investigated by density-functional theory with the generalized gradient approximation (GGA). The results indicate that increasing the coordination of indium atoms around the nitrogen, the competition between the nitrogen-nitrogen bond and the nitrogen-indium bond for In _nN _2 clusters, dominated by the former for n<7, is reversed for n≥7. The structure motif starts to transform from the structural characteristics of comprising N _2 unit to the characteristics with tetrahedral coordination of N atom from n=6 to 7, and then the N atom with a bulklike coordination emerges. By Mulliken population analysis, the results indicate that In-N bond shows a partial ionic character in the In _nN _2 clusters (n≥7). The calculated results on the averaged binding energy, second-order difference of cluster energies, the vertical ionization potentials as well as the HOMO-LUMO gaps of the In _nN _2 clusters (n=1-10) clusters indicate that the stability of In 8N 2 is the strongest of all the investigated clusters, due to stable cubic D _(2d) structure. The averaged binding energies of In _nN _2 are high in comparison to those of In _nN, implying that the stability of the clusters is remarkably enhanced by doping N.