Compressibility and crystal–fluid interactions in all-silica ferrierite at high pressure

Abstract

a b s t r a c tThe high-pressure behavior of a synthetic siliceous ferrierite has been studied by in situ single-crystal and powder synchrotron X-ray diffraction with a diamond anvil cell, using four different P-transmitting fluids: the non-penetrating silicone oil and the potentially pore-penetrating methanol:ethanol:H 2 O ¼ 16:3:1 mixture, ethylene glycol and 2methyl-2propen-1ol. The high-pressure experiment in silicone oil shows a remarkable flexibility of the FER framework. Two displacive phase transitions, following the path Pmnn-to-P12 1 /n1-to-P2 1 /n11 with pressure, were observed. The three polymorphs were found to share a virtually identical bulk compressibility, though showing a different anisotropic pattern. The experiments with potentially penetrating media enhanced the occurrence of a complex scenario, from which the P-induced intrusion of fluid molecules into the FER structural voids can be assumed by the different phase-transition paths and compressibility patterns, by the calculated residual electron density and by the different deformation mechanisms at the atomic scale, observed as a function of the used medium. The starting orthorhombic polymorph was always restored upon decompression in all the experiments. The roles of the different surface area in single crystal and polycrystalline samples, and of the process kinetics on the compressibility and crystalefluid interactions, are discussed.

Intrusion-extrusion experiments of MgCl2 aqueous solution in pure silica ferrierite: Evidence of the nature of intruded liquid by in situ high pressure synchrotron X-ray powder diffraction

“…The higher compression during XRPD experiment could have induced more defects in the Si-FER structure, leading to a partially irreversible behavior. A phase transition to the monoclinic symmetry P2 1 /n is observed for pressure values higher than 0.28 GPa, as already reported for compression experiments of Si-FER with other PTMs [29,43]. Upon pressure release from the highest P value to P amb , the system maintains the monoclinic symmetry, but another s.g. (P2 1 ) is argued.…”

“…The arise of new peaks (observed from 0.68 GPa) is due to the phase transition from Pmnn to P2 1 /n s.g. This phase transition has been observed in all the high pressure experiments performed on Si-FER, whatever the PTM employed [43].…”

“…silicone oil) [43], (V approximately equal to -10% in the same P range). This largely different elastic behavior is due to the penetration of the medium molecules, which contributes to stiffen the structure.…”

High‐pressure behavior and P‐induced phase transition of CaB3O4(OH)3·H2O (colemanite)

“…This behavior suggests that the strain of the borate chain along the a ‐axis (i.e., the less compressible direction among the three crystallographic axes) is accommodated by the tilting of the three‐membered rings around the shared O2 hinges. This is a common mechanism of strain accommodation adopted by different classes of materials, as, for example, the open‐framework silicates …”

Supramolecular Organization in Confined Nanospaces

“…Water‐alcohol mixtures of different composition are often used as pressure transmitting media. Mixtures of methanol/ethanol/water in proportions 16 : 3 : 1 are commonly adopted, and were also used in two high‐pressure investigations, on siliceous ferrierite. This confining matrix, according to experimental/computational studies, should be one of the most selective frameworks for the separation of water/alcohol mixtures – an important step in bioethanol production .…”