STRUCTURAL EVOLUTION OF Li-EXCHANED NATROLITE AT PRESSURE-INDUCED OVER-HYDRATION: AN X-RAY DIFFRACTION STUDY
Yu. V. Seryotkin1,2, A. Yu. Likhacheva1,3, S. V. Rashchenko1,2
1Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk National Research State University, Novosibirsk, Russia
3Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: цеолиты, Li-натролит, высокое давление, сверхгидратация, zeolites, Li-natrolite, high pressure, over-hydration
Abstract
The behavior of Li-exchanged natrolite Li1.92Na0.10[Al2.02Si2.98O10]x2H2O 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]x6H2O 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.
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