ANALYSIS OF WATER MOLECULES AND CATIONS DISTRIBUTION IN MONTMORILLONITE INTERLAYER BY MOLECULAR DYNAMICS SIMULATIONS

Abstract

It is important to establish computational methods for quantitatively predicting the montmorillonite swelling to understand the long-term mass transport behavior in geological disposal sites for high-level radioactive wastes. To this end, it is necessary to understand the hydration interaction between water and cation in the montmorillonite interlayer at the molecular scale. In this study, the distribution of interlayer water molecules and cations in Na- and Ca-montmorillonite were analyzed by molecular dynamics simulation to investigate the swelling characteristics of montmorillonite from the viewpoint of hydration structure. As a result, it was clarified that the water molecule coordination number of cations differs depending on the interlayer water content and cation species and that cations have hydration structures specific to the species and coordination number.