Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics

TL;DR

This paper develops a multiscale simulation approach combining all-atom MD and Brownian dynamics to efficiently model ion behavior in water, using a stochastic coarse-grained model parameterized from MD data.

Contribution

It introduces a coupled stochastic and ordinary differential equation model for ions, bridging detailed MD and simplified BD simulations in a multiscale framework.

Findings

The stochastic model accurately captures ion dynamics from MD data.

The multiscale method reduces computational cost while maintaining accuracy.

Application to ions in water demonstrates effectiveness.

Abstract

Molecular dynamics (MD) simulations of ions (K$^+$, Na$^+$, Ca$^{2+}$ and Cl$^-$) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parameterized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain.