“Nanocomposites and nanomaterials”

Ab initio study of the effect of metal doping on electronic properties of (ZnO)n (n= 96, 120) nanoclusters

R.V. Bovhyra1, D.I. Popovych1, O.V. Bovgyra2
1 Pidstryhach Institute for Applied Problems of Mechanics and Mathematics NAS Ukraine, Naukova 3-B, Lviv, Ukraine
E-mail: bovhyra@gmail.com
2 Ivan Franko National University of Lviv, Faculty of Physics, Kyrylo and Mefodiy 8, 79005-Lviv, Ukraine
The results of ab initio density functional theory studies of energy spectrum and ground state parameters of zinc oxide nanoclusters (ZnO)n (n = 96, 120), doped with different metals (Co, Cu, Ni) are presented. Calculations were performed using ultrasoft pseudopotentials in the basis of plane waves. To describe the exchange-correlation energy of the electrons, we used a generalized gradient approximation with Hubbard corrections (GGA+U) in Perdew, Burke and Ernzerhof parameterization. Optimization of the nanocluster structure was performed using conjugate gradient method. No symmetry restrictions were used during structure optimization.
The first task in this research, was figuring out the best placement position for the doping atoms. The two main configurations of the placement of Co, Cu and Ni atoms on the surface of the optimized (ZnO)96 and (ZnO)120 nanoclusters were considered: zinc atoms were substituted by the doping atoms; oxygen atoms were substituted by Co, Cu and Ni atoms. After relaxation procedure, the changes in the structural geometry of all studied nanosystems were observed. For the (ZnO)n+M(Zn) systems (n=96, 120; M=Co, Cu, Al) as well as (ZnO)n+M(O) (n=96, 120; M=Co, Cu, Al) systems, we observed significant drop in the energy gap value (Eg) compared to the pristine nanoclusters. Formation energy (Ef) was calculated for both placement positions researched in this study. The obtained results were then compared with the values obtained in our previous studies for (ZnO)n (n=34, 60) nanoclusters [1].
The negative values for the formation for (ZnO)n+M(Zn) indicate the exothermic character of the doping process while the positive formation energy value is corresponds to the endothermic process. Because of that, for our study the most favorable placement position for our doping atoms is configuration when a metal atom M (M=Co, Cu, Al) replaces the Zn atom.  
1.	Bovgyra R.V., Venhryn Yu.I., Serednytski A.S. et al. First principle study of electronic properties of ZnO nanoclusters with native point defects during gas adsorption. // Applied Nanoscience.-2022.-12, P.983-993.