Dresden 2009 – wissenschaftliches Programm
DF 9.2: Vortrag
Dienstag, 24. März 2009, 14:20–14:40, WIL B321
Understanding the nature of ion conductivity in inorganic systems — •Andreas Heuer1 and Heiko Lammert1,2 — 1Institut für Physikalische Chemie, WWU Münster — 2Center for Theoretical Biological Physics, San Diego
It is well accepted that the ion dynamics in inorganic ion conductors is based on ionic hops between adjacent sites provided by the network. It can be shown that the number of sites is only slightly larger than the number of ions . Thus, it has been speculated that the ion dynamics should be described as a vacancy rather than a particle dynamics. This approach is elucidated in this contribution. First, a quantification of the vacancy dynamics has to be achieved. Whereas this is trivial for lattice models, several complications arise for continous systems. In this way one can identify, e.g., the relevance of cooperative ion jumps, corresponding to vacancy jumps beyond the nearest neighbor shell. Second, from studying the distribution of waiting times of a specific site as well as the patterns of forward-backward jumps one finds that the vacancy dynamics can be basically described as a single-particle problem (in contrast to the ionic motion). This result justifies the use of single-particle models such as the random-energy model to describe ion dynamics. Third, it is checked that the macroscopic conductivity can be described within a single-particle approach for the vacancies.  H. Lammert, M. Kunow, A. Heuer, Phys. Rev. Lett. 90, 215901 (2003).