INFLUENCE OF DEFECTS ON ADSORPTION PROCESSES IN THE NEAR-SURFACE LAYERS OF ZnO NANOCLUSTERS: MD STUDY

We carried out molecular dynamics simulations to investigate the process of adsorption in the near-surface layers of ZnO nanoclusters. To describe the interaction between atoms, we used the reactive force field (ReaxFF). Two ZnO nanoclusters - one without defects and one with them - were the object of research. Several computer experiments with different initial conditions were performed. The study found that the defects have a significant effect on the structural and physical properties of ZnO nanoclusters, which is primarily due to the greater number of bonds in ZnO nanoclusters with defects than in pure ZnO. The adsorption process in different systems with different initial conditions occurred differently. It was found that the whole process of adsorption was divided into two stages: the first stage was characterized by a rapid increase in the number of adsorbed molecules, the second - an increase in fluctuations in the change of adsorbed molecules on the surface over time. The higher gas pressure in the system corresponds to a larger number of O-2 molecules, which diffuse into the volume of the ZnO nanocluster; therefore, the crystal structure of the surface of the ZnO nanocluster becomes amorphous. Also, it was found that the distribution of the dependence of the central symmetry parameter on the oxygen concentration in the system with a small amount of O-2 molecules was similar. The situation was completely different when the number of oxygen molecules increased: the value of the central symmetry parameter of the surface atoms was distributed more evenly, which cannot be considered as a crystalline state of the ZnO nanocluster.