Modeling Nucleation and Growth of ZnO Nanoparticles in a Low Temperature Plasma by Reactive Dynamics

Abstract

The very first stages of nucleation and growth of ZnO nanoparticles in a plasma reactor are studied by means of a multiscale computational paradigm where the DFT-GGA approach is used to evaluate structure and electronic energy of small (ZnO) N clusters (N ≤ 24) that are employed as a training set (TS) for the optimization of a Reactive Force Field (ReaxFF). Reactive Molecular Dynamics (RMD) simulations based on this tuned ReaxFF are carried out to reproduce nucleation and growth in a realistic environment. Inside the reaction chamber the temperature is around 1200 K, and the zinc atoms are oxidized in an oxygen-rich atmosphere at high pressure (about 20 atm), whereas in the quenching chamber where the temperature is lower (about 800 K) the ZnO embryo-nanoclusters are grown. The main processes ruling gas-phase nucleation and growth of ZnO nanoclusters are identified and discussed together with the dependence of the inception time and average stoichiometry of nanoclusters of different size on the composition of precursor material and physical parameters.

Effects of Gas-Phase Conditions and Particle Size on the Properties of Cu(111)-Supported ZnyOx Particles Revealed by Global Optimization and Ab Initio Thermodynamics

“…We should note that size effects are expected to persist for larger cluster sizes, given that free-standing and Ag-supported ZnO clusters exhibit marked size effects for sizes well above the ones considered here. In addition, there will likely still be lattice mismatch-related distortions even for very large monolayers, especially associated to reconstructions at the undercoordinated edge sites of the ZnO islands.…”

Reactive force field simulations of silicon clusters

“…Modelling plays a major role in unveiling the complex and interwoven processes which take place in a realistic reactor and a multi-scale approach becomes a fundamental tool to simultaneously guarantee a reliable level of accuracy and significant statistical sampling. The protocol used here has been designed for silicon but can be extended to other materials grown via plasma reactors, as in the case of zinc oxide [29].…”

“…All the simulations were carried out in the NVT ensemble at different temperature (Berendsen's thermostat) and composition. Before starting the production simulations, preliminary studies were conducted to calibrate required parameters such as dimension of the simulation box, thermostat, type of ensemble, integration time step, parametrization of the force field, temperature of the reactor, gas pressure (atomic density in the simulation box) and composition of the gas mixture, which could affect SiNPs growth rates and aggregation modes (for a detailed discussion see refs [23,29]. ).…”

Exploring the mechanisms of drug-delivery by decorated ZnO nanoparticles through predictive ReaxFF molecular dynamics simulations

“…S1 in the ESI †) was inspired by both the experimental characterizations of Cauda and coworkers, 12,13,29 who suggested spherical shapes and X-ray diffraction patterns similar to the single-phase wurtzite crystalline structure, and previous works of ours focused on partially crystalline nanoparticles (NPs) 30 and zinc oxide clusters. 31 The starting structure of the ZnONP was a truncated octahedron (spherical shape) made of 1419 Zn and 1419 O atoms (2838 atoms in all, randomly organized) with a maximum diameter of approximately 4 nm and different surface motifs. This was a sound prototype system that could confidently represent the whole dynamic behavior of the smaller experimental nanoparticles at reasonable computational times compatible with our HPC resources.…”