Exciton relaxation in KBr and CaF2 at low temperature: molecular dynamics study
Bibliographic record
Abstract
The results of a molecular-dynamics simulation of exciton relaxation in several ionic crystals at low temperature are reported. Both the lowest energy spin triplet and some of the low lying hole excited states are allowed to relax for the purpose of studying the radiation defect formation channels. The previously used semi-classical program has been modified to implement the solution of Newton’s equations with a 0.48 fs time step. The relaxation of an exciton localized on a single site (as Br0+e or F0+e, respectively) is studied at 10 K in KBr and in CaF2. In KBr the triplet self-trapped exciton leads to separated Frenkel pair in about 1–2 ps, followed by slow oscillation of the hole center along the (110) axis. The defect pair created is separated by about 10 Å (third-nearest neighbor). In CaF2, the relaxation reaches the geometry of the nearest Frenkel pair, with the hole center oriented along a (111) axis in about 0.3 ps at 10 K. However, at 80 K the system can undergo further relaxation into slightly more distant defect pairs. When the hole is excited to higher levels, the molecular bond of the hole center undergoes violent oscillations. In KBr, the hole center is found to form in the second-nearest-neighbor position within about 0.5 ps. The species formed are, however, different from the well-known primary radiation defects. A similar process is also observed in CaF2.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".