title: Relaxation in a Prototype Ionic Liquid: Influence of Water on the Dynamics.
abstract: The influence of water on the relaxation of a prototype ionic liquid (IL) C8mimBF4is examined in the IL-rich regime combining quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations. The QENS and MD simulations results for relaxation of IL and the equimolar mixture with water probed by the dynamics of the C8mim hydrogen atoms in the time range of 2 ps to 1 ns are in excellent agreement. The QENS data show that translational relaxation increases by a factor of 7 on the addition of water, while rotational relaxation involving multiple processes fitted by a KWW function with low β values is speeded up by a factor of 3 on the time scale of QENS measurements. The MD simulations show that the cation diffusion coefficient, inverse viscosity, and ionic conductivity increase on the addition of water, consistent with the very small change in ionicity. The difficulties in obtaining rotational and translational diffusion coefficients from fits to QENS experiments of pure ILs and IL-water mixtures are discussed.
authors.affiliation: CNRS, UPR 3079 and Université d'Orléans, Conditions Extrêmes et Matériaux: Haute Température et Irradiation, 1d avenue de la recherche scientifique, 45071 Orléans Cedex 2, France.
authors.forename: David L
authors.initials: DL
authors.lastname: Price
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory , Adelphi, Maryland 20783, United States.
authors.forename: Oleg
authors.initials: O
authors.lastname: Borodin
authors.affiliation: Institut Laue Langevin , 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: González
authors.affiliation: Institute for Solid State Physics, University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Kofu
authors.affiliation: Materials and Life Science Division, J-PARC Center, JAEA , Tokai, Ibaraki 319-1195, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shibata
authors.affiliation: Neutron R&D Division, CROSS-Tokai , Tokai, Ibaraki 319-1106, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Institute for Solid State Physics, University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamamuro
authors.affiliation: IMPMC-Université Pierre et Marie Curie and CNRS , 4 Place Jussieu, F-75252 Paris, France.|Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Marie-Louise
authors.identifier: http://orcid.org/0000-0002-0607-4815
authors.initials: ML
authors.lastname: Saboungi