Mechanism
of H<sub>2</sub>O Insertion and Chemical
Bond Formation in AlPO<sub>4</sub>‑54·<i>x</i>H<sub>2</sub>O at High Pressure
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Abstract
The
insertion of H<sub>2</sub>O in AlPO<sub>4</sub>-54·<i>x</i>H<sub>2</sub>O at high pressure was investigated by single-crystal
X-ray diffraction and Monte Carlo molecular simulation. H<sub>2</sub>O molecules are concentrated, in particular, near the pore walls.
Upon insertion, the additional water is highly disordered. Insertion
of H<sub>2</sub>O (superhydration) is found to impede pore collapse
in the material, thereby strongly modifying its mechanical behavior.
However, instead of stabilizing the structure with respect to amorphization,
the results provide evidence for the early stages of chemical bond
formation between H<sub>2</sub>O molecules and tetrahedrally coordinated
aluminum, which is at the origin of the amorphization/reaction process
