Ionic motion in materials with disordered structures

79th International Bunsen Discussion Meeting of the Deutsche Bunsen-Gesellschaft für Physikalische Chemie, Münster, Germany, 10–12 October, 2001.

Scope of the meeting

Ionic materials with disordered structures comprise structurally disordered crystals, ionic glasses and supercooled melts, as well as polymer electrolytes. These ionic systems differ greatly from ordinary crystalline materials, where point defects are isolated structural elements. With the entire matrix being disordered, ions tend to be particularly mobile. This qualifies disordered ionic materials for many applications in the field of Solid State Ionics, e.g. for advanced battery systems, fuel cells, and chemical sensors. While interest has recently focused on applications of disordered ionic materials, a better understanding of their structure and dynamics is certainly required to optimise their properties. What is more, the investigation of ionic motion in materials with disordered structures is also an important topic of basic research in its own right, defining the theme of the 79th International Bunsen Discussion Meeting.

The meeting was organised by Hellmut Eckert, Klaus Funke and Helmut Mehrer (all from Münster) and supported by Deutsche Forschungsgemeinschaft through SFB 458 (“Ionic Motion in Materials with Disordered Structures—from Elementary Steps to Macroscopic Transport”). The scientific leitmotif of the meeting, see the illustration on the front cover, is at the same time the logo of SFB 458. What at first sight seems to resemble the initials of Westfälische Wilhelms-Universität, is in effect a non-trivial, non-periodic, dynamic energy landscape in which mobile ions move from site to site. The ever-changing arrangement of the mobile ions gives rise to time-dependent interactions not only between the ions themselves, but also between the ions and the matrix. As a result, each ion feels a dynamic potential which determines its further motion. Evidently, this is an extremely complicated many-particle problem. In the lectures given at the meeting, the problem was viewed from different perspectives, and different approaches were presented towards its solution. This includes the study of the ion dynamics by targeted experiments and computer simulations, the development of model concepts and, last but not least, the synthesis and investigation of new disordered ionic materials.

Selected original research articles presented at the meeting are collected in this Special Issue of PCCP. This collection provides a comprehensive overview of the state of the art and also forms a basis for further research on diffusion mechanisms of ions in disordered materials.

Klaus Funke

Westfälische Wilhelms-Universität Münster and SFB 458

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