The behavior of Li-exchanged natrolite Li1.92Na0.10[Al2.02Si2.98O10]∙2H2O at compression in penetrating (water-containing) medium was studied by in situ synchrotron powder diffraction in diamond anvil cell up to 2.5 GPa. Within 0-1.3 GPa the compression is almost isotropic, and upon the further pressure increase the sample undergoes additional hydration, leading to abrupt volume expansion by 22%, a record value for natrolite. In the proposed model for the high-pressure phase Li2[Al2Si3O10]∙6H2O the Li+ cations have no contact with the framework O-atoms and are surrounded by “water-jacket” in the form of semi-octahedron (tetragonal pyramid) composed of five H2O molecules. Such polyhedra, lining up along the channel axis, are joined through their edges and create a “water” column expanding the structure.
- high pressure