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Nanowire versus nanotube: A quantum mechanical approach to some ZnO nanostructures and Cu/ZnO surface

Mina Ghiasi, Faezeh Farzaneh

Density functional theory with 6-31G basis set has been carried out in order to determine the geometric and electric structure of small ZnO nanostructures at room temperature. The calculations were done on ZnO nanowires and single-walled nanotubes with n atoms per periodic unit, where one periodic unit is made up of two hexagonal ZnO layers. The calculations show that, for small n, a single walled nanotube has lower energy than a nanowire but when the larger wire, have lower energy than SWNT.Also for large size of nanostructure the growth of nanowires in the z direction is more favorable than other x direction or x-y plane. Charge distributions of ZnO nanowire with 48 atoms are calculated, while top site adsorptions of Cu atoms on Zn or O atoms on the ZnO surface are considered. Optimized distances, charge transfers and binding energies associated with both types of adsorption processes are calculated. The interaction energies corrected by basis set super position error (BSSE) with the same level of calculation.