Insights from molecular dynamics simulations on structural organization and diffusive dynamics of an ionic liquid at solid and vacuum interfaces

Nataša Vučemilović-Alagić, Radha D. Banhatti, Robert Stepić, Christian R. Wick, Daniel Berger, Mario U. Gaimann, Andreas Baer, Jens Harting, David M. Smith (Corresponding author), Ana-Sunčana Smith (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)

Abstract

Hypothesis: A reliable modelling approach is required for simultaneous characterisation of static and dynamic properties of bulk and interfacial ionic liquids (ILs). This is a prerequisite for a successful investigation of experimentally inaccessible, yet important properties, including those that change significantly with the distance from both vacuum and solid interfaces. Simulations: We perform molecular dynamics simulations of bulk [C2Mim][NTf2], and thick IL films in contact with vacuum and hydroxylated sapphire surface, using the charge methods CHelpG, RESP-HF and RESP-B3LYP with charge scaling factors 1.0, 0.9 and 0.85. Findings: By determining and employing appropriate system sizes and simulations lengths, and by benchmarking against self-diffusion coefficients, surface tension, X-ray reflectivity, and structural data, we identify RESP-HF/0.9 as the best non-polarizable force field for this IL. We use this optimal parametrisation to predict novel physical properties of confined IL films. First we fully characterise the internal configurations and orientations of IL molecules relative to, and as a function of the distance from the solid and vacuum interfaces. Second, we evaluate densities together with mobilities in-plane and normal to the interfaces and find that strong correlations between the IL's stratification and diffusive transport in the interfacial layers persist for several nanometres deep into IL films.

Original languageEnglish
Pages (from-to)350-363
Number of pages14
JournalJournal of Colloid and Interface Science
Volume553
DOIs
Publication statusPublished - 1 Oct 2019

Keywords

  • Ionic liquid
  • Nano-scale film
  • Sapphire substrate
  • Interfaces
  • Molecular dynamics simulation
  • Non-polarizable force field
  • Sampling
  • Surface tension
  • X-Ray reflectivity
  • Structural order
  • Lateral diffusion
  • Residence time

Cite this

Vučemilović-Alagić, N., Banhatti, R. D., Stepić, R., Wick, C. R., Berger, D., Gaimann, M. U., Baer, A., Harting, J., Smith, D. M., & Smith, A-S. (2019). Insights from molecular dynamics simulations on structural organization and diffusive dynamics of an ionic liquid at solid and vacuum interfaces. Journal of Colloid and Interface Science, 553, 350-363. https://doi.org/10.1016/j.jcis.2019.06.017