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Journal of Structural Chemistry

2016 year, number 7

THE INFLUENCE OF EXTRAFRAMEWORK CATIONS ON THE BEHAVIOR OF K-EXCHANGED GONNARDITE AT HIGH PRESSURE

Yu. V. Seryotkin1,2, S. N. Dementiev1, A. I. Ancharov3
1Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk
2Novosibirsk State University, Novosibirsk
3Budker Institute of Nuclear Physics SB RAS, Novosibirsk
Keywords: цеолиты, K-гоннардит, K-натролит, высокое давление, сверхгидратация, zeolites, K-gonnardite, K-natrolite, high pressure, over-hydration

Abstract

The behavior of K-exchanged gonnardite K2,18Na0,04Ca0,02(H2O)2,2 [Al2,26Si2,74O10] at compression in penetrating water-containing medium was studied by synchrotron powder diffraction in diamond anvil cell. In contrast to the initial gonnardite, which exhibits the transition to high-hydrated paranatrolite at elevated humidity, its K-exchanged form is not capable of over-hydration even at high pressure. Within the whole studied pressure range (up to 4.8 GPa) the sample experiences the compression. At 3.5-4 GPa the compression anomaly is observed, which is interpreted as a phase transition accompanied by the symmetry lowering from tetragonal to monoclinic. The high-pressure structure evolution of K-exchanged forms of gonnardite and natrolite is compared; the difference in their behavior is explained by distinct configuration of the framework water-cation subsystem.