Random ion distribution model:: A structural approach to the mixed-alkali effect in glasses -: art. no. 132202

We have performed structural studies of a series of mixed-alkali phosphate glasses using diffraction experiments and reverse Monte Carlo simulations. We find that the alkali ions tend to preserve their local structural environment regardless of the glass composition. Furthermore, the distribution of the two types of cations in the structure is predominantly random. We propose that the long debated mixed-alkali effect is a natural consequence of the structural findings; a large energy mismatch for ionic jumps to dissimilar alkali sites resulting in blocking of low-dimensional migration pathways.