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Cubic High Pressure Paper_v2_unformated.docx (6.28 MB)
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Pressure-Induced Symmetry Changes in Body-Centered Cubic Zeolites

preprint
submitted on 12.12.2018 and posted on 13.12.2018 by Antony Nearchou, Mero-Lee Cornelius, Zoe Jones, Ines E. Collings, Stephen A. Wells, Paul R. Raithby, Asel Sartbaeva

Previous work has shown a strong correlation between zeolite framework flexibility and the nature of structural symmetry and phase transitions. However, there is little experimental data regarding this relationship, in addition to how flexibility can be connected to the synthesis of these open framework materials. This is of interest for the synthesis of novel zeolites, which require organic additives to permutate the resulting geometry and symmetry of the framework. Here, we have used high pressure powder X-ray diffraction to study the three zeolites: Na-X, RHO and ZK-5, which can all be prepared using 18-crown-6 ether as an organic additive. We observe significant differences in how the occluded 18-crown-6 ether influences the framework flexibility – this being dependant on the geometry of the framework. We use these differences as an indicator to define the role of 18-crown-6 ether during zeolite crystallisation. Furthermore, in conjunction with previous work we predict that pressure-induced symmetry transitions are intrinsic to body-centred cubic zeolites. The high symmetry yields fewer degrees of freedom, meaning it is energetically favourable to lower the symmetry to facilitate further compression.

Funding

Royal Society, URF

EPSRC, EP/K004956/1

ESRF beamtime

History

Email Address of Submitting Author

a.sartbaeva@bath.ac.uk

Institution

University of Bath

Country

UK

ORCID For Submitting Author

0000-0003-1017-0161

Declaration of Conflict of Interest

No conflict of interest

Version Notes

version 2 after all authours

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