Elastic behavior and high pressure-induced phase transition in chabazite: new data from a sample from Nova Scotia
Bibliographic record
Abstract
Recently, the high pressure (HP) behavior of a natural chabazite from Vallerano [1] (VALL), and on the synthetic \nphases SAPO-34 [1] and ALPO-34 [2], was investigated in the frame of a wider project aimed at understanding \nthe role of the framework/extraframework content on the compressibility of CHA-type porous materials. \nIn this work, further structural information is obtained studying the response to HP of another natural chabazite \nsample from Nova Scotia (Canada) (NS) (s.g. R-3mR [3]), characterized by a different chemical composition with \nrespect to VALL. The study was performed by means of in situ synchrotron X-ray powder diffraction (XRPD) and \nsilicone oil as non-penetrating P-transmitting medium. XRPD experiments were performed in DAC at the BM01 \nbeamline at ESRF (Grenoble, France) with a fixed =0.7355 Å. Powder patterns were collected from Pambup to 8.6 \nGPa and upon decompression. All the features of the Pamb pattern and the unit cell parameters are well recovered \nupon P release. Below 2.1 GPa, a and cell parameters slightly decrease and increase respectively with a resulting \nvolume reduction of 3.6 %. Above 2.1 GPa, a transition to a triclinic P-1 pseudo-rhombohedral phase is observed. \nThe rhombohedral to triclinic phase transition is accompanied by an abrupt decrease in the unit cell parameters and \nin the unit cell volume (V=-4.0%). Between 2.5 and 5.9 GPa, the triclinic/pseudo-rhombohedral cell parameters \ndecrease regularly and the unit cell volume variation (V=-3.0%) indicates a lower compressibility with respect to \nthat observed before the transition. In the highest P regime (5.9-7.2 GPa), a further slope change, with an increase \nin compressibility, is observed. As a whole, V between Pamb and 7.2 GPa is -12.6%. The elastic parameters, \ncalculated with a second order BM-EoS, are V0 = 826 (1) Å3, K0 = 54(3) GPa and V0 = 784(2) Å3, K0 = 91(5) \nGPa, for the rhombohedral and triclinic phase, respectively. \nPreliminary results from Rietveld refinements up to about 1 GPa, suggest that the deformation mechanism acting \nin the low-P regime is a cooperative tilting of the tetrahedra belonging to the double 6-ring – resulting in a decrease \nof its thickness – accompanied by a simultaneous di-trigonalization of the two 6-rings. A similar mechanism was \npreviously observed during compression of levyne [4]. \nThe HP-induced cell volume contraction of NS (12.6 %) is higher than that of VALL (10.3%) in the same P range. \nThis is congruent with the lower content in large extraframework potassium cations of NS, which contribute to \nsustain the porous structure in VALL. \n[1] L. Leardini, S. Quartieri, G. Vezzalini, Micropor. Mesopor. Mater. 127 (2010) 219-227 \n[2] L. Leardini, S. Quartieri, A. Martucci, G. Vezzalini, V. Dmitriev, Z. Kristallogr. (2012), doi: \n10.1524/zkri.2012.1477. \n[3] A. F. Gualtieri, E. Passaglia, Eur. J. Mineral. 18 (2006) 351–359. \n[4] G. D. Gatta, P. Comodi, P. F. Zanazzi, T. F. Ballaran, Am. Miner. 90 (2005) 645-652.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.003 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".