Quasi-elastic incoherent neutron scattering was used to study the diffusion of interlayer water in partially oriented Na-montmorillonite samples. In order to observe the anisotropy of the motion, measurements were performed for 2 orthogonal orientations and for 2 different energy resolutions. Fits to the spectra yielded phenomenonological translational line-widths which, for the 135º orientation, could be fitted by using a 2-dimensional Chudley-Elliott model; with a diffusion coefficient of 1.3 x 10-9m2/s and a mean-square jump distance of 0.17nm.

QINS Studies of Water Diffusion in Na-Montmorillonite. M.Gay-Duchosal, D.H.Powell, R.E.Lechner, B.Ruffle: Physica B, 2000, 276-278, 234-5