title: Fluctuating hydrodynamics for multiscale simulation of inhomogeneous fluids: mapping all-atom molecular dynamics to capillary waves.
abstract: We introduce a multiscale framework to simulate inhomogeneous fluids by coarse-graining an all-atom molecular dynamics (MD) trajectory onto sequential snapshots of hydrodynamic fields. We show that the field representation of an atomistic trajectory is quantitatively described by a dynamic field-theoretic model that couples hydrodynamic fluctuations with a Ginzburg-Landau free energy. For liquid-vapor interfaces of argon and water, the parameters of the field model can be adjusted to reproduce the bulk compressibility and surface tension calculated from the positions and forces of atoms in an MD simulation. These optimized parameters also enable the field model to reproduce the static and dynamic capillary wave spectra calculated from atomistic coordinates at the liquid-vapor interface. In addition, we show that a density-dependent gradient coefficient in the Ginzburg-Landau free energy enables bulk and interfacial fluctuations to be controlled separately. For water, this additional degree of freedom is necessary to capture both the bulk compressibility and surface tension emergent from the atomistic trajectory. The proposed multiscale framework illustrates that bottom-up coarse-graining and top-down phenomenology can be integrated with quantitative consistency to simulate the interfacial fluctuations in nanoscale transport processes.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California Berkeley, Berkeley, California 94720, USA.
authors.forename: Barry Z
authors.initials: BZ
authors.lastname: Shang
authors.forename: Nikolaos K
authors.initials: NK
authors.lastname: Voulgarakis
authors.forename: Jhih-Wei
authors.initials: JW
authors.lastname: Chu
mesh_terms: D001128:Argon / Q000737:chemistry*; D003198:Computer Simulation; D057446:Hydrodynamics; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D013500:Surface Tension; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D001128:Argon