Datasets:
pipeline/downfold.py: treat band occupations as per-spin fractions (n = 2·o) and select the band nearest half filling — fixes #15
Follow-up to #15 with a concrete patch and a reproducible before/after table.
What changes (pipeline/downfold.py, active_band()), two lines:
n_band = 2 * oinstead ofo— in a non-spin-polarized pw.x run the per-band<occupations>are
per-spin fractions in [0, 1]; the spin factor sits in the k-point weights, which this function
renormalizes to 1. (dos_at_ef()in the same file already multiplies by 2 for this reason.)- select the crossing band by
abs(2*o − 1.0)(nearest half filling) instead ofabs(o − 1.0), which in
[0, 1] picks the fullest band.
build_final.py needs no change: its particle–hole map (Ne > 36 → 72 − Ne) starts working oncen_band can exceed 1.
Two separable effects.
- Density interpretation — reproducible from the published table alone.
recompute_filling.pyreads the
existingn_bandcolumn as f, sets Ne = round(72 f) with the particle–hole map, and re-applies the
published A_d(δ). Output:active_challenge_corrected.csv. Top of the re-scored active set:
| new rank | old rank | material | n_band (per-spin) | old δ → score | corrected δ → score |
|---|---|---|---|---|---|
| 1 | 56 | CuS₂ (OSC-00581) | 0.478 | 0.556 → 0.0 | 0.056 → 22.6 |
| 2 | 57 | Co₂Se₂ (OSC-00102) | 0.512 | 0.500 → 0.0 | 0.000 → 16.4 |
| 3 | 47 | Cr₂N (OSC-01189) | 0.395 | 0.611 → 0.8 | 0.222 → 13.9 |
| 4 | 58 | CoO₂ (OSC-00925) | 0.471 | 0.556 → 0.0 | 0.056 → 13.7 |
| 5 | 39 | Cu₂Se₂ (OSC-00576) | 0.613 | 0.389 → 3.4 | 0.222 → 12.8 |
CHf₂ (33.2 → 7.2), CuBr₂ (22.0 → 2.8) and CuCl₂ (21.0 → 0.0) leave the top because their currently
selected bands are nearly full (f = 0.71–0.88, n = 1.4–1.8).
- Band re-selection — needs the SCF XMLs, so it is not reproduced here. It will change the active band
for most multi-band metals. From the C2DB band structures of six active materials (per-spin fillings
of all bands crossing E_F), the band nearest half filling gives:
| material | currently selected (f) | nearest-half band (f) | δ after fix |
|---|---|---|---|
| CHf₂ | 0.71 | 0.74 (only crosser besides 0.22) | ≈ 0.48 |
| CuBr₂ | 0.87 | 0.56 | ≈ 0.13 |
| CuCl₂ | 0.88 | 0.59 | ≈ 0.19 |
| Ni₂S₂ (2NiS-3) | 0.92 | 0.43 | ≈ 0.14 |
| CuS₂ | 0.48 | 0.43–0.48 | ≈ 0.04–0.15 |
| Co₂Se₂ | 0.51 | 0.55 | ≈ 0.09 |
So the Cu(II) halides stay on the dome with a different A_d, while CHf₂ does not.
Files
pipeline/downfold.py— the two-line change, with a comment.pipeline/recompute_filling.py— new; regenerates the corrected table from anyactive_challenge.csv+scoring_meta.json.validation/active_challenge_corrected.csv— output of the above on the current table (effect 1 only).
I have not touched active_challenge.csv or submissions.csv themselves; that is the organizers' call once
the XMLs are re-downfolded. Happy to adjust the patch if the pipeline's QE run used a convention I have not
seen.
🤖 Generated with Claude Code
Confirmed, and thank you — this is a correct and well-evidenced bug report. We reproduced it from the
published table alone and in our own pipeline code.
What we verified
pipeline/downfold.pyis internally inconsistent on the spin factor:dos_at_ef()multiplies by 2
(return 2.0 * n), butactive_band()renormalizes the k-weights to 1 and then uses the per-spin
band fractionodirectly as the site filling (n_band = o,delta = 1 - n_band), and selects the
crossing band byabs(o - 1.0). In a non-spin-polarized pw.x run the<occupations>are per-spin
fractions in [0,1] and the spin factor is in the k-weights (Σ = 2), so the density isn = 2oanddelta = |1 - 2o|.- Evidence reproduced from
active_challenge.csv: all 66n_bandvalues fall in [0.011, 1.007]
(only two marginally above 1.0), and the particle-hole remap is essentially never triggered — exactly
what a per-spin [0,1] quantity looks like, not a 0–2 density. - Chemistry check: CuCl₂ / CuBr₂ / CuI₂ (Cu²⁺, d⁹) are assigned
n_band= 0.884 / 0.873 / 0.862
("nearly full") where a half-filled x²−y² band (per-spin ≈ 0.5) is expected. - Re-scoring the published table with
n = 2oreproduces your #18 table exactly (CuS₂ 22.6, Co₂Se₂ 16.4,
Cr₂N 13.9, CoO₂ 13.7, Cu₂Se₂ 12.8).
Fix (both effects), applied to pipeline/downfold.py
n_band = 2 * o(site density; consistent withdos_at_ef)- select the crossing band by
abs(2*o − 1.0)(nearest half filling) instead of the fullest band build_final.pyneeds no change; its particle-hole map starts working oncen_bandcan exceed 1.
How we will roll it out
Because this changes the filling (hence A_d and the score) for every material, we are not hot-patching
the board silently. We will: (1) re-derive active_challenge.csv by re-reading the existing SCF outputs
with the corrected active_band() — no new DFT is needed; (2) publish the corrected pipeline and table
together with a short note so every participant's score moves under the same rule at the same time;
(3) re-express existing submissions against the corrected canonical values. The multi-band materials
(e.g. CHf2, which currently sits at #1 on the un-corrected filling) are resolved by the same change,
since the selector now targets the near-half-filled band rather than the fullest one.
Credit for finding and diagnosing this goes to @Yuseon84 (#15, #18), with the independent-reproduction
format we ask for. We will record the attribution in the dataset changelog when the corrected table ships.