Paper Number
SC15 James Swan Memorial Symposium
Session
Suspensions and Colloids
Title
The short and long time dynamics of concentrated electrolytes: a non-equilibrium Brownian Dynamics study*
Presentation Date and Time
October 10, 2022 (Monday) 4:45
Track / Room
Track 1 / Sheraton 4
Authors
- Krucker-Velasquez, Emily (Massachusetts Institute of Technology, Chemical Engineering)
- Swan, James W. (Massachusetts Institute of Technology, Chemical Engineering)
Author and Affiliation Lines
Emily Krucker-Velasquez and James W. Swan
Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
Speaker / Presenter
Krucker-Velasquez, Emily
Keywords
computational methods; colloids
Text of Abstract
The motion of ions in an electrolyte solution is described by the specific conductivity. The term conductivity is commonly associated with the response of an electrolyte solution to a steady electric field. However, a much richer study is that of the response to a transient or alternating field; such a study contains information pertaining to relaxation phenomena that control electrolyte transport. This non-equilibrium problem is challenging to investigate, particularly in concentrated electrolytes. Classical mean-field treatments of ions in solution rarely consider the volume occupied by the ions or the possibility of coupled fluxes. Moreover, in experimental settings, the ionic conductivity is by necessity measured indirectly due to additional physical phenomena, such as the presence of electric double layer structures in electrode-solution interfaces and electronic transport effects. This limits our ability to understand and characterize the bulk conductivity, forcing scientists and engineers to use phenomenological expressions when designing energy storage and delivery systems. It is in this context that particle-based simulation methods have emerged as useful tools to compute transport properties of electrolytes. Here, we investigate the frequency response of concentrated electrolytes using large scale Brownian dynamics simulations coupled with Poisson's equation. We study the short and long time dynamic response of ions in bulk by explicitly applying a sinusoidal electric field whose frequency increases exponentially with time. The analysis is performed both with and without inter-particle hydrodynamic interactions over a wide range of ionic concentrations; this allows us to characterize the long and short time dynamic response of electrolyte solutions and to identify scaling relationships for the dominant relaxation times of the frequency-dependent conductivity as a function of the Debye screening length. * This work is supported by NASA (Grant No. 80NSSC18K0162) and NSF (Career Award No. 1554398)