# Multiscale response of ionic systems to a spatially varying electric field

### Submission summary

 As Contributors: Jesper Schmidt Hansen Arxiv Link: http://arxiv.org/abs/1611.02131v3 Date accepted: 2017-04-23 Date submitted: 2017-02-22 Submitted by: Hansen, Jesper Schmidt Submitted to: SciPost Physics Discipline: Physics Subject area: Condensed Matter Physics - Theory Approaches: Theoretical, Computational

### Abstract

In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick's law, and a new constitutive relation for the mass flux due to the potential gradient is proposed. In the regime of low screening the response function due to the potential gradient is closely related to the ionic conductivity. In the large screening regime, on the other hand, the response function is governed by the charge-charge structure. Molecular dynamics simulations are conducted and the two wave vector dependent response functions are evaluated for models of a molten salt and an ionic liquid. In the low screening regime the response functions show same wave vector dependency, indicating that it is the same underlying physical processes that govern the response. In the screening regime the wave vector dependency is very different and, thus, the overall response is determined by different processes. This is in agreement with the observed failure of the Nernst-Einstein relation.

### Ontology / Topics

See full Ontology or Topics database.

Published as SciPost Phys. 2, 017 (2017)

Dear Editor

I hereby submit the revised version of the manuscript "Multiscale response of ionic systems to a spatially varying electric field".

Best regards Jesper

### List of changes

The changes are highlighted in red. Also, please refer to the reply to the referees.

### Submission & Refereeing History

Resubmission 1611.02131v3 on 22 February 2017
Submission 1611.02131v2 on 10 November 2016

## Reports on this Submission

### Anonymous Report 2 on 2017-3-24 Invited Report

• Cite as: Anonymous, Report on arXiv:1611.02131v3, delivered 2017-03-24, doi: 10.21468/SciPost.Report.100

### Report

I do not change my opinion about experimental realisation'' and the validity of the shifted Coulomb force method'', but the authour well reply to my questions and I can suggest the manuscript for publication.

### Requested changes

none

• validity: ok
• significance: ok
• originality: good
• clarity: good
• formatting: excellent
• grammar: excellent

### Anonymous Report 1 on 2017-3-22 Invited Report

• Cite as: Anonymous, Report on arXiv:1611.02131v3, delivered 2017-03-22, doi: 10.21468/SciPost.Report.98

### Strengths

1. The development of simple relations between dynamic properties in the presence of an external field and equilibrium properties of ionic systems is an interesting and important problem.

2. The authors proceeds to compute inputs to the theory from simulation.

3. Theory accurately reproduces numerical results.

4. Creates understanding of response functions in charged systems.

None

### Report

The author has adequately addressed the comments and concerns of both reviewers. I feel that the paper is now significantly improved and should be published.

### Requested changes

None

• validity: high
• significance: good
• originality: ok
• clarity: high
• formatting: excellent
• grammar: excellent