Figure 4
Alkali channels in mixed alkali CCRN Molecular Dynamics model of compensated alumino-silicate glasses. (A–D) Molecular graphics of the 1512 atom glass models with Al/Si = 1.0 (0 < X K < 0.75). Na (blue) and K (cyan) isosurfaces are represented using respective cut-off ionic radii of 1.24 Å and 1.64 Å. Both Na and K compensating metals cluster in the glasses, but percolation pathways are visible for X K > ~0.6 (D). See Fig. S6 for snapshots at T ~ T g (1100 K). (E–G) Molecular graphics of Al/Si = 0.33, 0.66, 1 and X K = 1.0 glass models, showing development of alkali clustering. (H) Enlargement of (G), illustrating Al-Al violation of Lowenstein’s Rule (Fig. 5B): Al (pink-white), Si (yellow), O (red). Melt ensemble sizes of 1512 atoms were also chosen to enable the extensive dynamics of network ions to be determined for all 15 melt models over 50 ns runs (Fig. 5F,G).
