Assessing different types of disorder in carbonate \nminerals with vibrational spectroscopy
Bibliographic record
Abstract
In this thesis, calcite was used as a test case to study the effects of structural disorder \non vibrational modes. Vibrational modes were examined using Fourier transform \ninfrared (FTIR) and Raman spectroscopy. Structural disorder was assessed by using \nX-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) measurements. \nData for temperature dependent FTIR, FTIR-photoacoustic (FTIR-PAS), and XAFS \nmeasurements were collected at the Canadian Light Source Inc. (Saskatoon, SK). \nFour normal vibrational modes of calcite were thoroughly investigated: the symmetric \nin-plane stretch (v₁, Raman active), out-of plane bend (v₂, IR active), asymmetric \nin-plane stretch (v₃, IR active), and in-plane bend (v₄, Raman and IR active). \nShapes of the v₁ and v₄ peaks are affected by long-range disorder and temperature, \nwhile the v₂ and v₃ peaks remain unchanged. By comparing the FTIR absorption \nspectra of different calcium carbonate polymorphs, we suggest that planar carbonate \narrangements are the key to cause v₄ broadening at higher temperatures and with \nstructural defects. \nTo explore the effects of structural defects in more detail, crystalline domain \nsize, lattice strain, and microstrain fluctuation values were calculated from XRD data. \nLong-range disorder strongly affects the vibrations in calcite. Bonding distances and \ncoordination environments in calcite based minerals (plasters) were assessed from \ntheir XAFS spectra. Results indicate that the local environments are dependent on the secondary phases (mainly Ca(OH)₂) in them. My thesis work demonstrates that \nparing FTIR with other techniques is more effective for researchers. \nWeak peaks related to the combination and isotopic modes in a calcite FTIR \nabsorption spectrum were also well studied. My thesis work demonstrates that weak \npeaks at 848 cm⁻¹ and 1398 cm⁻¹ in a FTIR absorption spectrum of calcite are due \nto the v₂ and v₃ vibrations of ¹³CO₃²⁻ rather than combination modes. These two \npeaks become stronger in spectra of calcite with a higher ¹³C concentration. Also, \nthe ratio between areas of the 848 cm⁻¹ peak and the ¹³CO₃²⁻ v₂ peak in a FTIR \ntransmittance spectrum match the natural abundance ratio of ¹³C:¹²C (near 1%). An \ninteresting phenomenon is that positions of these two peaks do not maintain with ¹³C \nconcentration changes. Theoretical calculations performed by our colleagues (Anna \nHirsch and Dr. Leeor Kronik, Weizmann Institute of Science, Israel) confirm my \nthesis results. \nMy thesis work shows that FTIR-photoacoustic (FTIR-PAS) spectroscopy is \nan appropriate technique to study weak isotopic and combination-mode peaks since \nthey are relatively enhanced under an acoustic detector. Origins of combination-mode \npeaks were discussed, and quantitative analyses of the ¹³C v₂ peak were carried out \nbased on FTIR-PAS spectra. A surprising finding is that the ¹³C v₂ mode presents \ncrystallinity dependency, while the ¹²C v₂ mode is not.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".