Surface-induced structural modification in ZnO nanoparticles

The majority of unusual properties of semiconductor nanoparticles arise both from quantum confinement effects or from surfaces effects. While the first one is reasonably well understood, very little is known about the effects of the surfaces on these nanostructures. In this manuscript, we have analyzed, by using ab initio methods based on the density functional theory, the structural modifications on the surfaces of ZnO nanoparticles smaller than 2 nm. We have observed a decrease in the bond distance between Zn and O atoms nearby the surface, and also a tendency for larger bond angles at these surfaces. This occurs to reduce the surface energy due to the presence of surface dangling bonds at the surfaces. These results should be important to help analyze experimental results.