The effect of temperatures of 0 to 150C was studied for homo-ionic montmorillonite clays with Na+ and Cs+ ions in low hydration states. Static and dynamic information concerning interlayer ions and water molecules was obtained using Monte Carlo and molecular dynamics. Marked differences were observed in the modes of diffusion of Cs+ and Na+ ions. The Cs+ ion exhibited clear site-to-site diffusion between sites allowing coordination to six oxygen atoms of the clay sheets. This behavior persisted up to high temperatures. Preferential sites for the Na+ counter-ion were significantly less well-defined even at low temperatures.

Na/Cs Montmorillonite: Temperature Activation of Diffusion by Simulation. N.Malikova, V.Marry, J.F.Dufrêche, P.Turq: Current Opinion in Colloid and Interface Science, 2004, 9[1-2], 124-7