Nanoscale physics

Simulations of the adsorption processes on ZnO nanoparticles by the molecular dynamics method 
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

We have analyzed the processes of O2, H2, CO gas adsorption on ZnO nanoclusters using the molecular dynamics method. We have selected Reactive Force Field (ReaxFF) as the interatomic potential for our study because of 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, 3]. 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. Structure of the surface of the ZnO nanocluster becomes amorphous with increasing concentration of gas molecules in the system. It was established that the tendencies of distribution of the dependence of the central symmetry parameter with the oxygen concentration were similar in the system less than 100 O2 molecules: they all had a pronounced peak in the range 0 - 4 A ̊, which indicates that they still maintain a relatively crystalline structure on their surface. However, the situation was quite different when the number of oxygen molecules increased: the value of the central symmetry parameter of surface atoms was more evenly distributed and there was one obvious peak in about 11 A ̊, which cannot be considered as a crystalline state of ZnO nanoparticle.

	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).
	3.Savka, S., Venhryn, Y., Serednytski, A. et al. Molecular dynamics simulation of adsorption processes on the surface of ZnO nanoclusters. Appl Nanosci (2021).