Characterization of ion distributions near the surface of sodium-containing and sodium-depleted calcium aluminosilicate melts

The distribution of cation and anion components of sodium calcium aluminosilicate was studied by classical molecular dynamics simulations in a high-temperature melt in the bulk and at the vacuum-melt interface. A significant redistribution of the sodium and non-bridging oxygen (NBO) ions was observed. Subsequently, a sodium depleted calcium aluminosilicate melt was simulated to determine the sensitivity of the redistribution of ions near the vacuum-melt interface to the presence of sodium ions. It is found that the thermodynamic equilibrium condition near the melt surface favors the enrichment of NBO ions that is closely associated with enrichment of the sodium ions.