Abstract
Elastic behavior and high-pressure (HP) structural evolution of a natural zeolite levyne, (Ca 0.5 ,Na,K) 6 (Al 6 Si 12 O 36 )·18H 2 O, has been investigated up to 5 GPa by means of in situ single-crystal X-ray diffraction with a diamond-anvil cell using a non-penetrating pressure-transmitting medium. Peculiar elastic behavior has been observed in the range 0–1 GPa: the c parameter decreases between 0 and 0.2 GPa, then increases up to 0.5–0.6 GPa. Above this P -value, the parameter decreases as expected. Anomalous behavior is also shown by the a -parameter, which first increases up to 0.2 GPa, then decreases as expected. However, these anomalous lattice variations are only slightly reflected in the cell volume behavior. The low- P trend ( P P > 1 GPa, refined with a second-order Birch-Murnaghan EoS, yields the following parameters: V 0 = 3539(3) A 3 and K T 0 = 48(1) GPa. Comparison of structural refinements performed at 0.0001, 0.79(5), and 3.00(5) GPa highlights two distinct deformation mechanisms of the Si/Al-framework, one predominant at low pressures (0–1 GPa) and the other at high pressures (1–5 GPa). The extra-framework content does not show any evident modification within the pressure range investigated.
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