Channel Diffusion in Sodium Silcate Melts

Kurzfassung

We used quasielastic neutron scattering and molecular dynamics simulations in order to study the interplay of intermediate range order, atomic dynamics and properties of mass transport in sodium silicate melts. Our results show that the sodium ions align in sodium rich channels that disrupt the Si-O structure and that form a percolation network. The sodium ions diffuse along these channels in a relatively immobile Si-O network. The diffusion via these channels results in a decoupling of incoherent from coherent correlations of the sodium relaxation, as evidenced by simulation and experiment. A characteristic length scale for this channel structure is marked by prepeaks in the elastic structure factors at about q = 0.9 Å-1, corresponding to length scales of the order of 7 Å.