Crystallographic Aspects of the CDW Instabilities in NbSe3
Bibliographic record
Abstract
Charge-density waves (CDW) in some quasi one-dimensional compounds can be depinned from the lattice by an external electric field. In the case of NbSe3, two CDW transitions have been reported with onset temperatures of 144 K and 59 K. From an analysis of the published low-temperature (LT) scanning tunneling microscopy (STM) images, which inherently allow the resolution of domain structures on the atomic scale, an alternative model of the CDW modulated structures in NbSe3 is proposed. In contrast to the existing model, where two incommensurate (IC) modes, q1 = (0,0.241,0) and q2 = (0.5,0.260,0.5) are selectively confined to two of three available structurally distinguished types of bi-capped trigonal prismatic columns, the alternative model [1,2] proceeds from the assumption that both columns of the same pair are alternatively modulated by the two modes, whose IC components add within experimental error into a commensurate value. The observed domains are formed as a result of the different bonding within and between the structural layers, separated by Van der Waals gaps, and of the ability of the two modes to be easily interchanged between two symmetry-related columns of the same type. This assumption is in accord with the published LT STM results, which confirm i.a. the presence of both IC modes above 59 K, where according to the previous model only the q1 contribution should be expected. A pair of two alternatively modulated columns of the same type represents the basic structural unit of the CDW ground state. The two modes can formally be replaced by a single inharmonic modulation, obtained by "beating" between the two IC modes.
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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 | 0.000 |
| 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".