Pressure-tuned spin chains in brochantite, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Cu</mml:mi> <mml:mn>4</mml:mn> </mml:msub> <mml:msub> <mml:mi>SO</mml:mi> <mml:mn>4</mml:mn> </mml:msub> <mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>OH</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:mn>6</mml:mn> </mml:msub> </mml:mrow> </mml:math>
Bibliographic record
Abstract
Using high-pressure single-crystal x-ray diffraction combined with thermodynamic measurements and density-functional calculations, we uncover the microscopic magnetic model of the mineral brochantite, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>Cu</a:mi> <a:mn>4</a:mn> </a:msub> <a:msub> <a:mi>SO</a:mi> <a:mn>4</a:mn> </a:msub> <a:msub> <a:mrow> <a:mo>(</a:mo> <a:mi>OH</a:mi> <a:mo>)</a:mo> </a:mrow> <a:mn>6</a:mn> </a:msub> </a:mrow> </a:math> , and its evolution upon compression. The formation of antiferromagnetic spin chains with the effective intrachain coupling of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>J</b:mi> <b:mo>≃</b:mo> <b:mn>100</b:mn> <b:mspace width="0.28em"/> <b:mi mathvariant="normal">K</b:mi> </b:mrow> </b:math> is attributed to the occurrence of longer Cu–Cu distances and larger Cu–O–Cu bond angles between the structural chains within the layers of the brochantite structure. These zigzag spin chains are additionally stabilized by ferromagnetic couplings <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:msub> <e:mi>J</e:mi> <e:mn>2</e:mn> </e:msub> </e:math> between second neighbors and moderately frustrated by several antiferromagnetic couplings that manifest themselves in the reduced Néel temperature of the material. Pressure tuning of the brochantite structure keeps its monoclinic symmetry unchanged and leads to the growth of antiferromagnetic <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mi>J</f:mi> </f:math> with the rate of 3.2 K/GPa, although this trend is primarily caused by the enhanced ferromagnetic couplings <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:msub> <g:mi>J</g:mi> <g:mn>2</g:mn> </g:msub> </g:math> . Our results show that the nature of magnetic couplings in brochantite and in other layered <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:msup> <h:mrow> <h:mi>Cu</h:mi> </h:mrow> <h:mrow> <h:mn>2</h:mn> <h:mo>+</h:mo> </h:mrow> </h:msup> </h:math> minerals is controlled by the size of the lattice translation along their structural chains and by the extent of the layer buckling.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.006 | 0.004 |
| Meta-epidemiology (narrow) | 0.004 | 0.008 |
| Meta-epidemiology (broad) | 0.002 | 0.007 |
| Bibliometrics | 0.002 | 0.005 |
| Science and technology studies | 0.005 | 0.006 |
| Scholarly communication | 0.006 | 0.006 |
| Open science | 0.009 | 0.009 |
| Research integrity | 0.006 | 0.006 |
| Insufficient payload (model declined to judge) | 0.473 | 0.010 |
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; both teacher heads agree on what is shown here.
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".