THE STRUCTURE OF INTERLAYER WATER IN A HYDRATED 2-1 CLAY

Neutron diffraction in conjunction with substitution of deuterium (D) for hydrogen (H) has been used to study the structure of water in a hydrated crystal of Ni-vermiculite. The intensities of the (00l) Bragg reflections were measured as a function of the H/D content, up to l=30. Difference analysis was then used to obtain separate density profiles, ρ{variant}(z), for the hydrogen and the oxygen plus the clay sheets. We have confirmed the existence of interlayer Ni2+ (H2O)6 complexes, in which the water molecules are strongly hydrogen bonded to the surface. More importantly, we have found that within the limits of the experiments all the additional water is located near the hexagonal rings of SiO4 and AlO4- tetrahedra, which comprise the surface. © 1990.