An in situ high-pressure single-crystal X-ray diffraction study of gobbinsite, the natural counterpart of the synthetic zeolite Na-P2, was carried out up to 4.3 GPa. No evidence of amorphization was observed within pressure-range investigated. Using a non-penetrating P-medium, two changes of the elastic behavior occur: the first at 1.1-1.3 GPa and the second at 2.7-3.2 GPa. Birch-Murnaghan equations of state truncated to the second order were used to fit the experimental P-V data within the three P-ranges (i.e. 0.0001-1.1, 1.3-2.7 and 3.2-4.3 GPa), giving the following isothermal bulk moduli (K-v0): 46.3(9), 52(8) and 28(6) GPa, respectively. The unit-cell compression is significantly anisotropic. In response to the applied pressure, the 8-membered ring channel parallel to [100] undergoes a significant increase of ellipticity, whereas the channel parallel to [010] undergoes a shrinking towards a circular shape at P >= 1.3 GPa. A partial re-organization of the H2O sites occurs between 1.1 and 1.3 GPa, and new framework deformational modes onset at P >= 3.2 GPa, coupled with a change in the coordination environment of the extraframework cations. (C) 2012 Elsevier Inc. All rights reserved.
On the high-pressure behavior of gobbinsite, the natural counterpart of the synthetic zeolite Na-P2
2012
Abstract
An in situ high-pressure single-crystal X-ray diffraction study of gobbinsite, the natural counterpart of the synthetic zeolite Na-P2, was carried out up to 4.3 GPa. No evidence of amorphization was observed within pressure-range investigated. Using a non-penetrating P-medium, two changes of the elastic behavior occur: the first at 1.1-1.3 GPa and the second at 2.7-3.2 GPa. Birch-Murnaghan equations of state truncated to the second order were used to fit the experimental P-V data within the three P-ranges (i.e. 0.0001-1.1, 1.3-2.7 and 3.2-4.3 GPa), giving the following isothermal bulk moduli (K-v0): 46.3(9), 52(8) and 28(6) GPa, respectively. The unit-cell compression is significantly anisotropic. In response to the applied pressure, the 8-membered ring channel parallel to [100] undergoes a significant increase of ellipticity, whereas the channel parallel to [010] undergoes a shrinking towards a circular shape at P >= 1.3 GPa. A partial re-organization of the H2O sites occurs between 1.1 and 1.3 GPa, and new framework deformational modes onset at P >= 3.2 GPa, coupled with a change in the coordination environment of the extraframework cations. (C) 2012 Elsevier Inc. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
