Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations
Bibliographic record
Abstract
Protonated and deuterated samples of the hydrogensulfide of cesium were studied by high-resolution neutron powder diffraction, calorimetry and proton NMR investigations in a wide temperature range. Primarily due to reorientational disorder of the anions, three modifications of the title compounds are known: an ordered low-temperature modification—LTM (tetragonal, I4/m, Z=8), a dynamically disordered middle-temperature modification—MTM (tetragonal, P4/mbm, Z=2), and a high-temperature modification—HTM (cubic, Pm3̄m, Z=1). The LTM⇄MTM phase transition is continuous. Its order parameter, related to an order/disorder and to a displacive part of the phase transition, coupled bilinearly, follows a critical law. The critical temperature TC=123.2±0.5 K determined by neutron diffraction of CsDS is in good agreement with TC=121±2 K obtained by calorimetric investigations. For the protonated title compound a shift to TC=129±2 K was observed by calorimetric measurements. The entropy change of this transition is (0.24±0.04) R and (0.27±0.04) R for CsHS and CsDS, respectively. The MTM⇄HTM phase transition is clearly of first order. The transition temperatures of CsHS and CsDS are T=207.9±0.3 K and T=213.6±0.3 K with entropy changes of (0.86±0.01) R and (0.81±0.01) R, respectively. Second moments (M2) of the proton NMR absorption signal of MTM and HTM are in reasonable agreement with M2 calculated for the known crystal structures. A minimum in spin-lattice relaxation times (T1) in the MTM could not be assigned by dipolar coupling to a two-site 180° reorientation of the anions, a model of motion presumed by the knowledge of the crystal structure. The activation enthalpies determined by fits of T1 presuming a thermal activated process are in the order of molecular reorientations (Ea=13.5±0.5 kJ mol−1 for the MTM and Ea=9.3±0.3 kJ mol−1 for the HTM). In the HTM at T>330 K translational motion of the cations determines T1 (Ea=13.8±0.4 kJ mol−1).
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".