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

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.