The structure of interlayer water in Li-montmorillonite studied by neutrondiffraction with isotopic substitution

We used neutron diffraction with an incident wavelength of 0.5024 Angstrom and both HD and Li-6/Li-nat isotopic substitution to study the structure of interlayer water in Li-Wyoming montmorillonite hydrates, with water conten ts corresponding to two-layer hydrates. The hydrogen isotope first-order di fference gives the weighted sum of partial structure factors and radial dis tribution functions related to the intra- and intermolecular structure arou nd interlayer water hydrogens. The results show unequivocally that the inte rlayer water adopts a liquid-type structure and that the clay surface does not prevent the interlayer water from adopting a highly hydrogen-bonded con figuration. The lithium isotope first-order differences for D2O and H2O hyd rates, and for the dry clay, are complicated by the presence of residual Br agg peaks. We discuss the possible origins of these features and the prospe cts for the further application of this technique to the study of hydrated clays.