An Overview of Microscopic Dynamics and Structure in Oxidic Melts

Despite of numerous investigations of oxidic melts and glasses using various experimental techniques in the past decades key features of macroscopic behaviour (e. g. dependance of viscosity or density on alkali concentration for a chosen network former) and their microscopic origin, even in the most simple binary compositions, are poorly understood. We present systematic investigations of oxidic melts containing various network-modifier (Na, K, PbO) as well as network-former (SiO_2, Al_2O_3, B_2O_3, PbO) by means of inelastic neutron scattering. We focussed our work on microscopic dynamics, structure and mass transport in alkali-silicate, Na-aluminosilicate, Na-borate, Na-germanate, and lead-silicate melts. Our investigations cover a dynamical range of 0.1 ps - 10 ns and momentum transfers of 0.2 - 2.2 A-1 at zero energy transfer, respectively. By using the interplay between inelastic neutron scattering and molecular dynamics simulations (access to similar time- and length-scales), performed by collaborating groups in Mainz and Montpellier (J. Horbach, W. Kob), we succeeded to attribute the mechanism of fast ion conduction and viscosity behaviour in sodium silicate melts to their structure.

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