Stefan Adams' abstract
Bragg Speaks Seminar
Wednesday 24 March 2010
11:00 am OPAL theatre B83
Structure – conductivity correlations in disordered solid electrolytes
Stefan Adams
National University of Singapore
Department of Materials Science and Engineering
Structure property function relationships provide valuable guidelines for a systematic development of functional materials. Utilizing a bond valence (BV) approach crystal chemical knowledge can be utilized to establish such relationships for disordered solid electrolytes. In the case of glassy solid electrolytes including mixed mobile ion glasses, the identification of the ion migration pathways and the analysis of their characteristics permits predictions of the transport properties from the structure model for a wide range of materials.For glasses the representative local structure models as a basis for the pathway analysis are derived from Reverse Monte Carlo fitting to X-ray and neutron diffraction data or from Molecular Dynamics simulations, which provides the opportunity to compare the prediction of the bond valence “energy landscape” from a snapshot of the structure model with an analysis of a complete trajectory. Recently we have worked out the link between the bond valence mismatch and the absolute energy scale so that the parameters can now also be used as force-fields for MD simulations, where simulation and pathway analysis can be based on the same parameter set. Examples for the application of this approach will focus on low cost, high performance cathode materials such as olvine-type LiFePO4 or LiFeSO4F exploring the effect of defect engineering on the dimensionality of Li+ transport, as well as the mechanism of the experimentally observed drastic conductivity enhancement in nanoscale heterostructures such as LixFePO4 nanocrystals with a glassy Li4P2O7 surface layer.