Field-dependent ionic conductivities from nonequilibrium molecular dynamics simulations

Advances in the fabrication of nanofluidic devices have enabled the study of transport processes on small scales, where novel phenomena emerge from the interplay between confinement, fluctuations and molecular granularity. Some of the most striking recent observations have been in electrokinetic transport of electrolyte solutions confined to nanometer dimensions, where nonlinear effects are often recorded. [1-5]
We develop a formalism and a numerical approach to efficiently compute the electric field dependent conductivity of electrolytes. [6] Specifically, we derive a relationship for the latter in terms of molecular fluctuations that is valid arbitrarily far from equilibrium. Moreover, we devise a novel nonequilibrium reweighting approach that provides access to rare dynamical fluctuations within nonequilibrium molecular dynamics simulations. We investigate bulk solutions of differing ionic strengths, differing implicit solvent conditions and the effect of water as a solvent.

[1] S. J. Kim, Y.-C. Wang, J. H. Lee, H. Jang, and J. Han, Physical review letters 99, 044501 (2007).
[2] R. Karnik, C. Duan, K. Castelino, H. Daiguji, and A. Majumdar, Nano letters 7, 547 (2007).
[3] W. Guan, R. Fan, and M. A. Reed, Nature communications 2, 506 (2011).
[4] U. Vermesh, J. W. Choi, O. Vermesh, R. Fan, J. Nagarah, and J. R. Heath, Nano letters 9, 1315 (2009).
[5] J. Feng, K. Liu, M. Graf, D. Dumcenco, A. Kis, M. Di Ventra, and A. Radenovic, Nature materials 15, 850 (2016).
[6] D. Lesnicki, C. Y. Gao, B. Rotenberg and D. Limmer, Physical review letters 124, 206001 (2020).