Heterogeneous multiscale method for high energy-density matter: Connecting kinetic theory and molecular dynamics

• Published in: Journal of Computational Physics: X 2020-09, Vol.8, p.100070, Article 100070
• Main Authors: Shohet, Gil, Price, Jacob, Haack, Jeffrey, Marciante, Mathieu, Murillo, Michael S.
• Format: Article
• Language: English
• Subjects: Heterogeneous multiscale method; Kinetic theory; Molecular dynamics; Multiscale; Plasma modeling
• ISSN: 2590-0552; 2590-0552
• DOI: 10.1016/j.jcpx.2020.100070

•Molecular dynamics provides closure data to a kinetic model at the macroscale.•Collisional effects are captured far more accurately than by kinetic theory alone.•Plasma relaxation processes are computed much faster than by molecular dynamics alone.•Kinetic models can be extended to multispecies systems far from equilibrium. We have developed a concurrent heterogeneous multiscale method (HMM) framework with a microscale molecular dynamics (MD) model and a macroscale kinetic Vlasov-BGK model. The kinetic model is formulated such that BGK collision times are the closure data obtained from MD. Using the H-theorem, we develop the mathematical link between the MD and the kinetic model. We examine three relaxation processes, energy, momentum, and bump-on-tail, using full microscale MD simulations as a reference solution. We find that solutions computed with the HMM framework offer a significant computational reduction (14×−100×) compared with computing a full MD solution, with significant improvements in accuracy compared with a kinetic model using analytical collision times.