Structures and Stability of Iron Halides at the Earth’s Mantle and Core Pressures: Implications for the Missing Halogen Paradox
Bibliographic record
Abstract
The terrestrial abundance of heavy halogens Cl, Br, and I is depleted by approximately one order of magnitude relative to those predicted on the basis of their volatilities. One plausible explanation for this missing halogen paradox is their sequestration into the Earth’s core. Therefore, heavy halogens in the core may combine with the dominant element, Fe, to form iron halides that potentially exert important effects on the properties and dynamic evolution of the Earth’s inner core. In this study, stable iron halide phases have been predicted from first-principles structural searches at four pressures corresponding to those at the Earth’s mantle and core. At 360 GPa (corresponding to the inner core), the most stable iron chloride is CsCl-type FeCl, supporting the hypothesis that light-element impurities can stabilize the body-centered cubic Fe structure. At pressures of the Earth’s core, it is also observed that the chemical nature of iodine changes from an electron acceptor to an electron donor. This change results in an enhancement of the stability and the formation of a novel Fe2I compound containing a Fe–I framework with linear Fe chains intercalated in the open channels. Thus, the role of pressure in determining the stoichiometry of stable high-pressure halides is demonstrated by our theoretical calculations. These findings suggest the possibility of thermodynamic stability of iron halides in the assemblage in the Earth’s inner core.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".