Molecular dynamics evaluation of self-diffusion coefficients in two-dimensional dusty plasmas

We employ the Green-Kubo (G-K) and Einstein relations to estimate the self-diffusion coefficients (denoted as D_G and D_E, respectively) in two-dimensional (2D) strongly coupled dusty plasmas (SC-DPs) via equilibrium molecular dynamics (EMD) simulations. D_G and D_E are computed for a broad domain of screening length (κ) and coupling parameters (Γ) along with different system sizes. It is observed that both D_G and D_E decrease linearly with increasing Γ in warm liquid states and increase with increasing κ. In cold liquid states, the Einstein relation accurately predicts D_E in 2D SC-DPs because diffusion motion is close to normal diffusion, but the G-K relation provides overestimations of D_G, because VACF indicates anomalous diffusion; thus, D_G is not accurate. Our new simulation outcomes reveal that D_G and D_E remain independent of system sizes. Furthermore, our investigations demonstrate that at higher temperatures, D_G and D_E converge, suggesting diffusion motion close to normal diffusion, while at lower temperatures, these two values diverge. We find reasonable agreement by comparing current and existing numerical, theoretical and experimental data. Moreover, when normalizing diffusion coefficients by the Einstein frequency and testing against the universal temperature scaling law, D_G deviates from theoretical curves at low temperatures and κ, whereas D_E only disagrees with theory at very small κ (≃ 0.10). These findings provide valuable insight into diagnosing dust component parameters within 2D DP systems and contribute to the broader understanding of diffusion processes in DP environments.