Adsorption energy of SPC/E water in silicalite, as a function of the partial charge on silicon. The framework is hydrophobic for . The dashed and the dot-dashed lines show, respectively, the vaporization enthalpy of the SPC/E model of water (Ref. 39) and the smallest experimental adsorption energy of water in silicalite (Ref. 6).
6-exp potential wells in the BKS model (Ref. 9) (thin lines) and optimized here for (thick lines). The well-known “” catastrophe of 6-exp functions (Ref. 36), visible at the left of the figure, can be suppressed if necessary by addition of an appropriate term where and .
Simulated temperature dependence of the cell volume of cristobalite (arrow shows order of simulations).
Simulated monoclinic to orthorhombic transition of silicalite, model: (a) Cell sides, shown for convenience of plotting as: (◼), (●), (◆); (b) cell angles: (◼), (●), (◆).
Longest principal axes (arrows) of the most anisotropic oxygen thermal ellipsoids in the model silicalite (average over all atoms in the full simulation folded into one unit cell). (a) View parallel to along the zigzag channels; (b) view along the straight channels parallel to .
(a) Adsorption energies of a single water molecule in silicalite, with the force field. (b) Adsorption sites corresponding to the energies (green), and (blue), viewed down the axis.
Log-log plot of the mean squared displacements along (solid line), (dashed line), and (dot-dot-dashed line) of a SPC/E water molecule diffusing in silicalite (flexible model) at 300 K. The inset shows the same mean squared displacements in silicalite with a frozen framework.
Structural and elastic properties of -quartz. Experimental values at low temperature and results of energy minimizations with the original and the modified BKS models.
Force field parameters for SPC/E water in silicalite (BKS model).
silica force field parameters.
Experimental and simulated properties of -cristobalite.
Unit cell parameters of silicalite obtained in unconstrained minimizations, starting from the orthorhombic and the monoclinic structures.
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