Molecular dynamics studies on the role of tetramethylammonium cations in the stability of the silica octamers Si8O8-20 in solution

被引:35
作者
Caratzoulas, S [1 ]
Vlachos, DG
Tsapatsis, M
机构
[1] Univ Delaware, Dept Chem Engn, Newark, DE 19716 USA
[2] Univ Minnesota, Dept Chem Engn & Mat Sci, Minneapolis, MN 55455 USA
关键词
D O I
10.1021/jp0500891
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The stability of silica octamers, Si8O208- observed in tetramethylammonium (TMA) solutions by Kinrade et al. (Inorg. Chem. 1998, 37, 4272) is investigated in connection with the TMA concentration by performing equilibrium molecular dynamics simulations of Si8O208--TMA-water mixture at two concentrations. At the experimental concentration at which the silica octamers have been observed spectroscopically, we find that, on the average, six TMA molecules surround the silica octamer, coordinated so that each cation occupies a face of the cubic octamer. We also find that upon TMA adsorption, water molecules associated with the siloxane oxygens leave the silica surface, whereas the hydrogen-bond network of the silanol oxygens with water molecules remains intact. No TMA adsorption is observed at the concentration at which the octamers have not been observed.
引用
收藏
页码:10429 / 10434
页数:6
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