Berlin 2008 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 20: Glasses III (joint session DF/DY)
DY 20.6: Vortrag
Mittwoch, 27. Februar 2008, 15:45–16:00, EB 407
Ion Dynamics in Room Temperature Ionic Liquids — Monika Mutke, •Radha Dilip Banhatti, and Klaus Funke — Institut für Physikalische Chemie und SFB 458, Universität Münster, Corrensstr. 30, D-48149 Münster
Room temperature ionic liquids (RTIL) are molten salts consisting of a bulky organic cation such as 1-butyl-3-methyl-imidazolium (BMIM) and anions such as BF4− and PF6−. Above TG, RTILs exhibit non-Arrhenius type DC conductivities and are classified as of intermediate fragility. Earlier, the broadband conductivity spectra of a fragile ionic melt [1] and of a polymer electrolyte [2] were modelled providing a link between the short-time and the long-time dynamics of the ions, via the dispersive features of the spectra. We could thus obtain the activation energy of the elementary displacive step, E*. In this contribution, we present and analyse the conductivity spectra of BMIMBF4 from 1 mHz up to about 6 GHz in the temperature range 193 K - 353 K. We show that BMIMBF4 exhibits spectral features similar to those of the polymer electrolyte, indicating the importance of structure mediated ion-ion interactions. Moreover, both for BMIMPF6 and BMIMBF4, E* is found to be about 0.18 eV, which is similar to the conformational reorientation energy of the cation [3].
[1] P. Singh, R.D. Banhatti and K. Funke, Phys. Chem. Glasses 46, 241 (2005).
[2] S.J. Pas, R.D. Banhatti and K. Funke, Solid State Ionics 177, 3135 (2006).
[3] A. Rivera and E. Rössler, Phys. Rev. B 73, 212201 (2006).