Marian PALUCH1, Wojnarowska ZANETA1
1University of Silesia, Institute of Physics, KATOWICE, Poland
Recently, a fascinating idea called the thermodynamic or density scaling was proposed to jointly describe the dependence of molecular dynamics of glass-forming liquids on thermal and packing effects [1, 2]. According to this idea, both isobaric and isothermal data can be expressed as a single universal curve if they are plotted against the new variable TVγ, where T and V denote temperature and specific volume, respectively, and γ is the scaling exponent. This presentation focuses on analyzing the electrical conductivity of several ionic liquids (ILs) measured at different temperatures and pressures in terms of the density scaling concept [3]. Our results clearly show that for all studied ILs, the scaling exponent is a state-point independent parameter that can be related to the exponent in the inverse power law describing the repulsive part of the effective short-range potential for intermolecular interactions [4]. It will also be shown how the idea of density scaling can be applied to analyze entropy data. However, in this case, the scaling exponent is no more a state-point independent parameter and is equivalent to Grüneisen parameter. Interestingly, for all tested samples, a linear relationship between Grüneisen parameter (scaling exponent) and entropy was obtained, and more importantly, the generated slope shows a close relation to the typical interactions (van der Waals and Coulomb forces, and H-bonds). Therefore, we establish a new correlation for this group of compounds.
References
[1] G. Floudas, M. Paluch, A. Grzybowski, and K. L. Ngai, Molecular Dynamics of Glass-Forming Systems: Effects of
Pressure: Advances in Dielectrics, Springer-Verlag, Berlin 2011
[2] A. Grzybowski, M. Paluch, The Scaling of Relaxation Processes: Universality of Density Scaling Ch, vol. 4, Springer, Berlin, 2018.
[3] M. Paluch, Dielectric properties of ionic liquids, Springer 2016
[4] Z. Wojnarowska, M. Musia?, M. Dzida and M. Paluch, Phys. Rev. Lett. 123, 125702 (2019)