1 research outputs found
Anisotropic Features of Water and Ion Dynamics in Synthetic Na- and Ca-Smectites with Tetrahedral Layer Charge. A Combined Quasi-elastic Neutron-Scattering and Molecular Dynamics Simulations Study
The temperature- and orientation-dependent dynamics of
water molecules
and sodium or calcium cations confined in the interlayer space of
synthetic saponite with contrasting layer charge were analyzed through
the combination of three-axis neutron spectroscopy and molecular dynamics
(MD) simulation. We first show that it is possible to generate MD
simulated quasi-elastic spectra that are equivalent to the experimental
ones. As a consequence, the analysis of spectra in terms of Lorentzian
decomposition can be advantageously replaced by a direct exploitation
of MD results. We show that such strategy provides classical information
on the influence of clay crystal chemistry on water and ion dynamical
features as well as reliable additional information on (i) dynamics
associated to different types of water molecules (bonded or not to
interlayer cations) and (ii) interlayer cation dynamics. The same
strategy applied to data obtained at higher temperature provided further
confirmation of the validity of the atomic potentials used in simulations
while allowing the extraction of activation energies for water and
cations translational motions