Adsorption of an Mn atom on a ZnO sheet and nanotube: a density functional theory study.

First-principles calculations based on density functional theory were performed to study the stable geometries, electronic structure and magnetic properties of the adsorption of a single Mn atom on a graphitic ZnO sheet and a (9, 0) single-wall ZnO nanotube. For the graphitic ZnO sheet, the Mn atom prefers to reside above the center of a hexagon (H site), with a relatively large binding energy of 1.24 eV. The H site is also the most stable site for adsorption of an Mn atom inside the ZnO nanotube, with a large binding energy of 1.47 eV. In both of these cases, the total magnetic moment is 5.0 μ(B) per Mn atom, which is the same as that of a free Mn atom. When the Mn atom is adsorbed outside the tube, the most energetically favorable site is the atop oxygen site. The magnetic moment is 3.19 μ(B) for this configuration. The smaller magnetic moment is mainly due to the strong p-d mixing of O and Mn orbitals. The different adsorption behaviors are related to the curvatures of the nanostructures.