Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Wells, Stephen A.; Sartbaeva, Asel; Gatta, G. Diego

doi:10.1209/0295-5075/94/56001

Cited by 22 publications

(25 citation statements)

References 25 publications

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“…Remarkably, our results are even sensitive to Al/Si ordering in the framework. Geometric simulations for wairakite, which displays Al/Si ordering, match the experimental data when ordering is included but not when a uniform average T-O distance is used [13].…”

Section: Ana Group Zeolitesmentioning

confidence: 84%

“…Locations of the phase transitions of wairakite (W) and leucite (L) are indicated by arrows. Modified from [13] Fig. 2 P-V data for analcime (green triangles) and pollucite (red squares) annotated with results of geometric simulation.…”

Section: Silicalitementioning

confidence: 99%

“…Locations of the phase transitions of analcime (A) and pollucite (P) are indicated by arrows. Modified from [13] Fig. 3 P-V data for silicalite with (green circles-CO 2 , red triangles-Ar), without (open diamonds) penetrating pressure medium.…”

Section: Silicalitementioning

confidence: 99%

See 2 more Smart Citations

Framework flexibility and rational design of new zeolites for catalysis

Sartbaeva

Wells

2012

Appl Petrochem Res

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Zeolite materials have proved very useful as chemical catalysts and the search for new zeolite structures with novel channel and pore shapes is ongoing. We discuss a geometric feature of zeolite frameworks, the flexibility window, which may provide a criterion to identify hypothetical structures which can be synthesised as zeolites. In recent research using data on zeolite frameworks under compression, we show strong links between this geometric feature and the physics of zeolite frameworks.

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Section: Ana Group Zeolitesmentioning

confidence: 84%

Section: Silicalitementioning

confidence: 99%

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Framework flexibility and rational design of new zeolites for catalysis

Sartbaeva

Wells

2012

Appl Petrochem Res

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“…Using geometric simulation we have shown that this transition occurs when the structure reaches the edge of its cubic flexibility window [41]. This insight extends to other minerals with the ANA framework—leucite, pollucite and wairakite [42]—and in wairakite, Al/Si ordering in the framework is significant [43]. …”

Section: Applications Of Geometric Analysis and Simulationmentioning

confidence: 89%

Template-Based Geometric Simulation of Flexible Frameworks

Wells

Sartbaeva

2012

Materials

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Specialised modelling and simulation methods implementing simplified physical models are valuable generators of insight. Template-based geometric simulation is a specialised method for modelling flexible framework structures made up of rigid units. We review the background, development and implementation of the method, and its applications to the study of framework materials such as zeolites and perovskites. The “flexibility window” property of zeolite frameworks is a particularly significant discovery made using geometric simulation. Software implementing geometric simulation of framework materials, “GASP”, is freely available to researchers.

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“…This idealization of the zeolite framework, as a periodic truss of rigid tetrahedra, has led to several insights into their structural properties. Zero-frequency RUMs have been discovered, and their role in phase transitions and the absorption properties of framework materials has been investigated [15,16,[29][30][31]. It has also been discovered that all of the known zeolite frameworks are flexible, exhibiting a range of densities over which volume changes are absorbed by tetrahedral rotations, without generating any stresses [19,21].…”

Section: Zeolites As Three-dimensional Periodic Trussesmentioning

confidence: 99%

Flexibility mechanisms in ideal zeolite frameworks

Treacy

Kapko

Rivin

2014

Phil. Trans. R. Soc. A.

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Zeolites are microporous crystalline aluminosilicate materials whose atomic structures can be usefully modelled in purely mechanical terms as stress-free periodic trusses constructed from rigid corner-connected SiO 4 and AlO 4 tetrahedra. When modelled this way, all of the known synthesized zeolite frameworks exhibit a range of densities, known as the flexibility window, over which they satisfy the framework mechanical constraints. Within the flexibility window internal stresses are accommodated by force-free coordinated rotations of the tetrahedra about their apices (oxygen atoms). We use rigidity theory to explore the folding mechanisms within the flexibility window, and derive an expression for the configurational entropic density throughout the flexibility window. By comparison with the structures of pure silica zeolite materials, we conclude that configurational entropy associated with the flexibility modes is not a dominant thermodynamic term in most bulk zeolite crystals. Nevertheless, the presence of a flexibility window in an idealized hypothetical tetrahedral framework may be thermodynamically important at the nucleation stage of zeolite formation, suggesting that flexibility is a strong indicator that the topology is realizable as a zeolite. Only a small fraction of the vast number of hypothetical zeolites that are known exhibit flexibility. The absence of a flexibility window may explain why so few hypothetical frameworks are realized in nature.

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Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Cited by 22 publications

References 25 publications

Framework flexibility and rational design of new zeolites for catalysis

Framework flexibility and rational design of new zeolites for catalysis

Template-Based Geometric Simulation of Flexible Frameworks

Flexibility mechanisms in ideal zeolite frameworks

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