A Discrete Ion Stochastic Continuum Overdamped Solvent Algorithm for Modeling Electrolytes

In this talk we present a methodology for the mesoscale simulation of fluid/particle systems such as strong electrolytes. This is an extension of the Fluctuating Immersed Boundary (FIB) approach that treats a solute as discrete Lagrangian particles that interact with Eulerian hydrodynamic and electrostatic fields. In both cases the Immersed Boundary (IB) method of Peskin is used for particle-field coupling. Hydrodynamic interactions are taken to be overdamped, with thermal noise incorporated using the fluctuating Stokes equation, including a "dry diffusion" Brownian motion to account for scales not resolved by the coarse-grained model of the solvent. Long range electrostatic interactions are computed by solving the Poisson equation, with short range corrections included using a novel immersed-boundary variant of the classical Particle-Particle Particle-Mesh (P3M) technique. This approach is designed to enable scaling to large problems which are difficult to tackle using many existing mesoscale methods. It has been implemented using the AMReX framework for use on large scale HPC systems, including heterogeneous CPU+GPU architectures.