The partitioning of Dy and Tb in NdFeB magnets: A first-principles study
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Bibliographic record
Abstract
Doping with Dy/Tb is a current solution to improve the coercivity and the operating temperature of NdFeB magnets, by increasing the magnetocrystalline anisotropy of the (Nd, Dy/Tb)2Fe14B (2:14:1) phase. The efficiency of Dy/Tb doping depends on the distribution of Dy/Tb in the multi-phase microstructure of the NdFeB magnet. To understand and control the Dy/Tb redistribution, the partitioning of Dy/Tb between 2:14:1 and Nd-rich phases has been studied by a first-principles density functional calculation. The total energy calculations indicate that Dy and Tb prefer to enter the 4f sites in the 2:14:1 phase. The substitution energies of Dy and Tb in 2:14:1 are negative and are −0.35 eV/atom and −0.33 eV/atom, respectively, as Nd is replaced with 25% of Dy/Tb, i.e., stabilizing the 2:14:1 structure. However, the substitution energies of Dy and Tb in NdO have large positive values. They are 0.83 eV/atom and 0.73 eV/atom for Dy and Tb, respectively, when 25% of Nd is replaced by Dy/Tb. The results indicate that Dy/Tb prefer to enter the 2:14:1 phase rather than the Nd-rich phase (NdO). This is the thermodynamic origin for the selective occupation of Dy and Tb in the 2:14:1 structure which enhances the magnetic anisotropy field.
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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 | 0.001 | 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it