Molecular Simulation of Aqueous Electrolytes in Silica Nanochannels

Aqueous electrolytes, NaCl and CaCl₂, in silica nanochannels with radius ranging from 0.67 nm to 1.5 nm were simulated with the molecular dynamics technique. An atomistic wall model and the SPC/E water model were used in the simulations. The effects of radius and charge on the wall surface of the nanochannel were studied. The self-diffusivity of water molecules and ions along the axial direction of nanochannel was calculated. It was shown that water molecules form different layers when the radius of the nanochannel changes. The effects of the wall on the movement of water molecules and ions are related to the radius of the nanochannel. The charges on the wall surface exert little influence on water molecules and chloride ions while effect positive ions greatly. Surface charges were neutralized by positive ions, which were essentially immobilized at the surface charge sites.