(110c) A Continuum-Atomistic Hybrid Simulation of Droplet Spreading On a Flat Solid Surface

A moving contact line plays a central role in the spreading of liquid droplets on solid surfaces. In the continuum description of droplet spreading, assumptions are made regarding slip at the moving contact line. However, molecular phenomena governing contact-line motion cannot be easily incorporated into continuum models. Molecular dynamics (MD) simulations can provide microscopic information at the contact line, but are prohibitively expensive to implement for drop sizes of practical interest. With the aim of tackling this dilemma, we developed a continuum-MD hybrid method to investigate spreading dynamics of droplets on flat solid surfaces. The continuity and Navier-Stokes equations are solved using the finite-volume method in a continuum domain comprised of the main body of the drop excluding a small region (particle domain) in the vicinity of the moving contact line. Atomistic MD simulations are used to determine fluid behavior in the particle domain. The spatial coupling between the continuum and particle domains is achieved through constrained dynamics of flux continuities in an overlap domain. We compare the results of the hybrid algorithm with those of full atomistic simulations for nanodroplet spreading on a flat surface to validate the hybrid method. We employ our model to investigate the coupling between molecular and continuum length scales in droplet spreading.