The surface and size effects on the structural stability and electronic properties of InAs one-dimensional nanostructures are investigated by first-principles calculations within density functional theory. No matter what the diameters, the nanowires are more energetically favorable than the nanotubes due to the preferable sp3 hybridization for In and As atoms in the InAs nanostructures. The formation energies of these nanostructures satisfy a linear dependence relationship with the surface atom ratio. The calculated band structures reveal that the band gaps of InAs nanostructures are determined by two competition mechanisms. One is the quantum confinement effect, which favors the increase of the band gaps with the decreasing diameter or wall thickness. Another is the effect of surface dangling bonds, which induces the decrease of the band gaps with the decreasing diameter or wall thickness. With the same diameter, the band gaps of InAs nanowires are still less than those of the nanotubes. The result indicates that the quantum confinement effect in one-dimensional structures can be enhanced by the formation of tubes instead of wires.

The size-dependent electronic, structural and magnetic properties of AgnFe (n ⩽ 15) clusters have been investigated by using the density functional theory (DFT) within the generalized gradient approximation. The starting structures were generated from empirical genetic algorithm simulations. The most stable structures were then selected from a number of structural isomers based on the results of the further DFT calculations. The atom prefers to stay at the centre of the clusters. The 2D to 3D transition occurs at n = 6. The magnetic properties and the geometric structures are strongly correlated. For , the total magnetic moment of the cluster is quenched. The reason is similar to the Kondo effect in bulk metal. Also, is considered to be very stable according to the 18-electron counting rule.

The bare M and ligand-protected nanoparticles M(25)(SR) and M(13)(PR)(10)Cl (M = Au, Ag, Cu) are investigated using the density functional theory. There are strong interactions between the metal core atoms and the ligands. It is found that the electronic structures agree well with the Jellium model for gold and copper nanoparticles. The superatoms's S and P orbitals are shown. However for silver ones, as the adding of the ligands, the S orbital of the nanoparticle disappears. The binding energy of these nanoparticles are also obtained by our calculation. The Au nanoparticles are most stable, the Cu ones take second place, and the Ag ones are the third stable. Our results could be essential for further understanding of the properties of ligand-protected isolated superatoms.

The stability and the optical band gap of the Zinc Oxide clusters (ZnO)n (n = 2-18) are investigated by using density functional theory (DFT) and the time-dependent density functional theory (TD-DFT), respectively. The differences between the HOMO-LUMO gap (delta(h-l)) and the optical gap (delta(opt)) are dramatic for small clusters (2 < or = n < or = 5). As the increasing of the cluster size, the differences become small. The results indicate that the stability and the optical gap are related to the sizes and symmetries of the clusters. Further, it is shown that the structures have much greater impact on the optical gap, there is the dipole-forbidden transition in the optical gap for high symmetric structures.

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