Nanoscale physics

Molecular dynamics simulations of the adsorption processes on ZnO nanoclusters
S.S. Savka 1, D.I. Popovych 1, A.S. Serednytski 1
1 Pidstryhach Institute for Applied Problems of Mechanics and Mathematics NASU, Naukova str., 3b, Lviv-79060, Ukraine.
E-mail: savka.stepan.92@gmail.com

In this paper, we have analyzed in detail the processes of O2, H2 gas adsorption on ZnO nanoclusters using the molecular dynamics method. By analyzing the nature of the formation of such nanostructures and referring to sources about the interatomic potentials, we have selected Reactive Force Field (ReaxFF). This interatomic potential has been developed for a wide range of chemical compounds, including ZnO, and already has been used by us in previous work [1, 2]. To study the main parameters, the gas pressure in the system, the size of ZnO nanoparticles, and the system temperature were changed. At high temperatures, small nanoclusters began to melt at the initial moments of modeling, and when too large nanoclusters were selected, the modeling times became very long, which did not allow to trace the evolution of the system to the final moment of modeling. Therefore, there was a need to choose the optimal initial conditions. A key point of the simulation is the communication between system and the thermostat to maintain a specific system temperature. Since a significant amount of energy was released during the oxidation of nanoclusters, such connection is necessary to avoid further temperature rises. In real experiments, this connection is provided by an inert or reactive gas. The total energy of the system and radial distribution functions (RDF) were used to describe the adsorption processes. Our results show that the whole adsorption process can be divided into two stages. Structure of the surface of the ZnO nanocluster becomes amorphous with increasing concentration of gas molecules in the system. 

 1.	S.S. Savka, D.I. Popovych, A.S. Serednytski, Molecular Dynamics Simulations of the Formation Processes of Zinc Oxide Nanoclusters in Oxygen Environment, Nanophysics, Nanomaterials, Interface Studies, and Applications. NANO 2016. Springer Proceedings in Physics 195 (2016) 145-156.
 2.	S.S. Savka, Yu.I. Venhryn, A.S. Serednytski, D.I. Popovych, Molecular Dynamics Simulations of the Formation Processes and Luminescence Properties of Zn-ZnO Core-Shell Nanostructures // Jouranl of Nano- and Electronic Physics 10 (2018) 03008(5).