Molecular Dynamics Simulation of Water Confinement in Disordered Aluminosilicate Subnanopores

Takahiro Ohkubo (1) , S. Gin (2) , Marie Collin (2) , Yasuhiko Iwadate (1)

1 Chiba University
2 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

The porous structure and mass transport characteristics of disordered silicate porousmedia are significantly different from those in ordered porous media. The aim of thisstudy was to investigate the gaps between nanometer-scale ordered and disordered poresby means of a geometry-based analysis of the porous structure and water dynamics.Our approach to building disordered silicate porous media involved tracing the realdissolution behavior of an alkali aluminoborosilicate glass, i.e., soluble Na and B wereremoved from the bulk glass, and then water molecules and some Na were introducedinto the pores according to an experimental observation. This procedure provides arealistic complex porous structure filled with water. Large discrepancies between thesurface areas of ordered and disordered porous media were found the geometry-basedanalysis. In addition, we observed a number of isolated water molecules in the poresdespite accessible porous connectivity. The fraction of mobile water was approximately1percent, the main dynamics of water correspond to vibrational motion in a confined space.This phenomenon is due to strong interactions resulting from the large surface area,which significantly reduce water mobility. Our original setup and analyses in this studyprovide a solution for predicting the porous structure and water transport characteris-tics of disordered silicate porous media.

Keywords: disordered porous structure; subnanopore; molecular dynamics

Domains: Nuclear Experiment [nucl-ex]; Nuclear Theory [nucl-th]

Takahiro Ohkubo, S. Gin, Marie Collin, Yasuhiko Iwadate. Molecular Dynamics Simulation of Water Confinement in Disordered Aluminosilicate Subnanopores. Scientific Reports, 2017, 8, pp.3761. ⟨10.1038/s41598-018-22015-3⟩. ⟨cea-02421746⟩