A Network Approach to Unravel Correlated Ion Pair Dynamics in Protic Ionic Liquids. The Case of Triethylammonium Nitrate

TL;DR

This study uses network theory and molecular dynamics to analyze ion pair correlations in triethylammonium nitrate, revealing local correlations and vibrational relaxation dynamics without long-range effects.

Contribution

It introduces a network-based analysis of correlated ion pair motions in protic ionic liquids using molecular dynamics simulations.

Findings

Local correlations occur when two cations share the same anion.

N-H bond vibrational relaxation time is approximately 5.3 ps.

Energy redistribution remains nonspecific and does not propagate long-range correlations.

Abstract

The intermolecular interactions in the title compound are investigated using self-consistent charge density functional based tight binding molecular dynamics. Emphasis is put on the analysis of correlated motions of ion pairs using ideas of network theory. At equilibrium such correlations are not very pronounced on average. However, there exist sizeable local correlations for cases where two cations share the same anion via two NHO-hydrogen bonds. The effect of an external perturbation, which artificially introduces a sudden local heating of an NH-bond, is investigated using nonequilibrium molecular dynamics. Here, it is found that the average N-H bond vibrational relaxation time is about 5.3 ~ps. This energy redistribution is rather nonspecific with respect to the ion pairs and does not lead to long-range correlations spreading from the initially excited ion pair.