Molecular Dynamics simulations of low temperature plasma processing

As plasma processes are atomic and molecular by nature, simulations at the molecular level will be relevant for providing us with insights into core and interface plasma chemistry basic phenomena. Moreover, statistical averaging allows to provide/predict macroscopic data as reaction rates, diffusion coefficients, ... directly comparable with experiment outputs. Among all the available molecular simulation tools, (reactive) molecular dynamics (MD) simulation technique is a good compromise between quantum mechanical and kinetic Monte-Carlo methods, especially due to the availability of robust and accurate reactive force fields [1]. Moreover, such reactive forcefields are also calculating partial chages at any relevant times using charge equilibration algorithm. In the context of plasma chemistry this will allow to adress charge transfer mechanisms. Using this forcefields, MD simulations are able to calculate the trajectories of a set of particles, by solving the appropriate set of Newton equations of motion. For realistic comparisons with experiments, inputs of MD simulations have to be selected for matching experimental conditions. 

Addressing reactive plasma processes remains a quite challenging and useful task. Two examples nicely illustrate the interest of carrying out reactive molecular dynamics simulations:  i) Hydrocarbon plasma deposition, including plasma phase reactivity [2] and ii) plasma-liquid interaction, especially effects of plasma produced reactive oxide and nitride species on organic molecules in water [3]. Both methodological aspects of MD simulation implementation for these plasma processes and determination of statistical data directly comparable with experiments will be reviewed.

References

[1] E. C. Neyts, P. Brault, Plasma Process. Polym. 14 (2017) 1600145

[2] D. Graves, P.Brault, J. Phys. D: Appl. Phys. 42 (2009) 194011

[2] P. Brault et al, J. Appl. Phys. 129 (2021) 183304