Nataša Vučemilović-Alagić1, Radha D Banhatti2, Robert Stepić3, Christian R Wick4, Daniel Berger5, Mario U Gaimann6, Andreas Baer7, Jens Harting8, David M Smith9, Ana-Sunčana Smith10. 1. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: nvucemil@irb.hr. 2. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia. Electronic address: Radha.Dilip.Banhatti@irb.hr. 3. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: Robert.Stepic@irb.hr. 4. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: christian.wick@fau.de. 5. Forschungszentrum Jülich GmbH, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy, Fürther Straße 249, 90429 Nürnberg, Germany. Electronic address: Daniel.x.berger@googlemail.com. 6. PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: Mario.gaimann@gmx.de. 7. PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: Andreas.baer@fau.de. 8. Forschungszentrum Jülich GmbH, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy, Fürther Straße 249, 90429 Nürnberg, Germany. Electronic address: j.harting@fz-juelich.de. 9. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia. Electronic address: dsmith@irb.hr. 10. Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address: smith@physik.fau.de.
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.
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.
Authors: Nataša Vučemilović-Alagić; Radha D Banhatti; Robert Stepić; Christian R Wick; Daniel Berger; Mario U Gaimann; Andreas Baer; Jens Harting; David M Smith; Ana-Sunčana Smith Journal: Data Brief Date: 2019-11-23