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 machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".