GEC Student Excellence Award Finalist Presentation - Can PIC simulations be used for atmospheric pressure plasmas? Impact of strong correlations

The particle-In-Cell (PIC) method is a cornerstone in plasma modeling because it offers a way to simulate entire plasma devices. It makes kinetic simulation tractable by representing a very large number of physical particles as individual macroparticles interpolated to a grid. The accuracy of this approximation hinges on the plasma being weakly coupled. Here, molecular dynamics simulations are used as a first-principles benchmark to test the applicability of PIC to cold atmospheric pressure plasmas (CAPP). Results show that because ions reach moderate and strongly coupled regimes, PIC is not well suited to CAPP. For example, the approximation of having multiple macroparticles per cell misses important physical effects such as disorder-induced heating that significantly influences plasma and gas temperatures. In order to capture this effect, PIC must apply a restrictive condition of a grid resolution that resolves the interparticle spacing. Furthermore, a unity macroparticle weight is essential to avoid an artificial increase in the average Coulomb potential energy, which can affect the plasma temperature. When operated this way, PIC essentially operates as an MD method and the computational cost renders it impractical for device-scale modeling. Attempts to decrease the computational cost by reducing spatial dimensions are found to exacerbate these problems.