Computer simulation of water molecules at kaolinite and silica surfaces

Abstract

Molecular dynamics simulations of water molecules at the surface of kaolinite, and of amorphous silica, have been carried out. In contrast to previous work, clay and silica atoms are not kept fixed at their crystallographic positions; all atoms are allowed to move. In both cases water molecules at the surface show a marked decrease in the self-diffusion coefficient and an increase in the rotational correlation time. We consider the effects of increasing the ionic strength of the water. Comparison with experimental data is made by linking calculated diffusion and rotational correlation times to available pulse field gradient nuclear magnetic resonance spectroscopy and relaxation measurements.