Theoretical Study Of The Structure, Stability And Cu Doping Effects Of Zn_nO_n (n=1-13) Clusters

With the rapid progress in density functional theory (DFT) and its numerical methods, First-principle calculation based on DFT has become a vital method for condensed matter physics, quantum chemistry and material science. ZnO is a multifunctional material which has excellent performance in various aspect. It has attracted considerable attention due to its unique combination of material properties and wide range of applications to light-emitting diodes, laser, piezoelectric materials, chemical sesors, solar cells and so on. Recently ZnO clusters and its 3d transitional metal doping nanostructures have been synthesized and exhibits potential prospects in many areas. In order to find the structural properties of ZnnOn clusters and their doping mechanism, we have investigated the geometrical and electrical structures of ZnnOn (n=1-13) clusters and the effects of doping Cu atoms via full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) and DMOL3 method.We have performed systematic search and calculation for ZnnOn (n=1-13) clusters. Some new ground state structures are found and some are the same as the former report.The geometrical structures of ZnnOn clusters demonstrate a certain degree of regularity as the cluster size increases. For n≤7, the ground state structures of ZnnOn clusters are ring structures with the Zn atom and O atom alternating arrangement, while cage structures become dominant for n=9-13. n=8 may proved to be a crossover from ring to tube/cage structures. In order to verify the stability and electronic properties of the ZnnOn clusters, we calculated the binding energy for per atom, the second difference of energy of the lowest energy structures, we have found that the ZnnOn clusters at n=3,9, and 12 possess relatively higher stability. When n>3, the clusters show bigger HOMO-LUMO gaps.As for Cu doped ZnnOn clusters, we choose clusters at n=3,9,12 as doping basis, the structural and magnetic properties are studied via different doping numbers. We have found that monodoped clusters retain a magnetic moment of 1μB which is incorrelative to its geometry and energy. The magnetic moment was mainly contributated by the polarized 3d state of Cu atoms and 2p state of O atoms through Mulliken Population ananlysis. For bidoped clusters, the magnetic moment due to Cu-Cu interaction.