Add dataset card with full column descriptions and usage

README.md

@@ -1,64 +1,112 @@
----
-license: cc-by-4.0
-configs:
-- config_name: default
-  data_files:
-  - split: train
-    path: data/train-*
-dataset_info:
-  features:
-  - name: immutable_id
-    dtype: string
-  - name: bawl_hasher
-    dtype: string
-  - name: elements
-    list: string
-  - name: nsites
-    dtype: int64
-  - name: chemical_formula_anonymous
-    dtype: string
-  - name: chemical_formula_reduced
-    dtype: string
-  - name: chemical_formula_descriptive
-    dtype: string
-  - name: nelements
-    dtype: int64
-  - name: dimension_types
-    list: int64
-  - name: nperiodic_dimensions
-    dtype: int64
-  - name: lattice_vectors
-    list:
-      list: float64
-  - name: cartesian_site_positions
-    list:
-      list: float64
-  - name: species_at_sites
-    list: string
-  - name: compressed_charge_density
-    list:
-      list:
-        list: float64
-  - name: compressed_aeccar0_density
-    list:
-      list:
-        list: float64
-  - name: compressed_aeccar1_density
-    list:
-      list:
-        list: float64
-  - name: compressed_aeccar2_density
-    list:
-      list:
-        list: float64
-  - name: bader_charges
-    list: float64
-  - name: bader_atomic_volume
-    list: float64
-  splits:
-  - name: train
-    num_bytes: 17496189623
-    num_examples: 69117
-  download_size: 9385266248
-  dataset_size: 17496189623
----
+---
+license: cc-by-4.0
+tags:
+  - materials-science
+  - dft
+  - charge-density
+  - r2scan
+  - bader
+  - crystal-structure
+---
+
+# LeMat-Rho
+
+**LeMat-Rho** is a dataset of ~69,000 inorganic crystal structures computed with the **r2SCAN meta-GGA functional** in VASP, featuring charge densities, Bader charges, forces, stresses, and energies. It is part of the [LeMaterial](https://huggingface.co/LeMaterial) ecosystem.
+
+## Dataset Summary
+
+| Property | Value |
+|---|---|
+| Materials | 69,117 |
+| Functional | r2SCAN |
+| Sources | AFLOW (agm), OQMD (oqmd-), Materials Project (mp-) |
+| Bader charge coverage | 86.2% (59,613 materials) |
+| Charge density grid | 15×15×15 (lossy compressed via pyrho) |
+| DDEC6 charges | Planned for future release |
+
+## Sources
+
+| Source | Materials |
+|---|---|
+| AFLOW (`agm*`) | 38,925 |
+| OQMD (`oqmd-*`) | 29,611 |
+| Materials Project (`mp-*`) | 581 |
+
+## Workflow
+
+Each material was computed with a 4-step VASP pipeline:
+
+1. **PreStaticMaker** — initial single-point on unrelaxed geometry
+2. **RelaxMaker_1** — geometry relaxation (r2SCAN)
+3. **RelaxMaker_2** — second relaxation pass (r2SCAN)
+4. **StaticMaker** — final NSW=0 single-point; source of all reported properties
+
+Forces, stresses, and energies are from the final static calculation. Charge densities (CHGCAR, AECCAR0, AECCAR1, AECCAR2) are from the StaticMaker output.
+
+Bader charges were computed using the [Bader charge analysis code](http://theory.cm.utexas.edu/henkelman/code/bader/) (Henkelman group) with AECCAR0+AECCAR2 as the reference charge density.
+
+## Columns
+
+| Column | Type | Unit | Description |
+|---|---|---|---|
+| `immutable_id` | string | — | Unique material identifier (e.g. `agm001234567`) |
+| `elements` | list[string] | — | Element symbols present |
+| `nelements` | int | — | Number of distinct elements |
+| `nsites` | int | — | Number of atoms in the unit cell |
+| `chemical_formula_reduced` | string | — | Reduced formula (e.g. `Fe2O3`) |
+| `chemical_formula_anonymous` | string | — | Anonymous formula (e.g. `A2B3`) |
+| `chemical_formula_descriptive` | string | — | Full descriptive formula |
+| `lattice_vectors` | list[list[float]] | Å | 3×3 lattice matrix |
+| `cartesian_site_positions` | list[list[float]] | Å | Atomic positions |
+| `species_at_sites` | list[string] | — | Element at each site |
+| `functional` | string | — | DFT functional (`r2scan`) |
+| `energy` | float | eV | Total DFT energy (final static) |
+| `energy_corrected` | float | eV | Energy with MP2020 corrections (equals `energy` for r2SCAN) |
+| `forces` | list[list[float]] | eV/Å | Per-atom forces from final static |
+| `stress_tensor` | list[list[float]] | kBar | 3×3 stress tensor from final static |
+| `bader_charges` | list[float] | e | Bader net charges per atom (positive = cationic); null if AECCAR files absent |
+| `bader_atomic_volume` | list[float] | ų | Bader atomic volumes per atom |
+| `ddec6_charges` | list[float] | e | DDEC6 net charges per atom (null in current release; planned) |
+| `compressed_charge_density` | string | — | Lossy-compressed CHGCAR (15×15×15 grid, JSON-encoded via pyrho) |
+| `compressed_aeccar0` | string | — | Lossy-compressed AECCAR0 (core charge density) |
+| `compressed_aeccar1` | string | — | Lossy-compressed AECCAR1 |
+| `compressed_aeccar2` | string | — | Lossy-compressed AECCAR2 (valence charge density) |
+| `charge_density_grid_shape` | list[int] | — | Grid dimensions [nx, ny, nz] |
+| `space_group_it_number` | int | — | International Tables space group number |
+| `bawl_fingerprint` | string | — | Structure fingerprint (BAWL hasher) |
+| `magnetic_moments` | list[float] | μ_B | Per-atom magnetic moments (null if not spin-polarized) |
+| `total_magnetization` | float | μ_B | Total cell magnetization |
+| `cross_compatibility` | bool | — | Cross-compatibility flag with other LeMaterial datasets |
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("LeMaterial/LeMat-Rho", split="train")
+
+# Filter to materials with Bader charges
+with_bader = ds.filter(lambda x: x["bader_charges"] is not None)
+print(f"Materials with Bader charges: {len(with_bader)}")
+
+# Access a material
+row = ds[0]
+print(row["chemical_formula_reduced"], row["bader_charges"])
+```
+
+## Notes
+
+- **Charge density compression**: The stored charge densities are lossy-compressed to a 15×15×15 grid using [pyrho](https://github.com/materialsproject/pyrho). This is suitable for qualitative analysis and ML feature extraction but not for quantitative integration (e.g. re-running Bader). The raw CHGCAR files are available on request.
+- **Bader coverage**: ~13.8% of materials lack Bader charges because their AECCAR files are absent from the source S3 data. This is consistent across all three source databases and reflects an upstream calculation issue.
+- **DDEC6 charges**: `ddec6_charges` is null in this release. A follow-up patch run is planned.
+- **r2SCAN functional**: All calculations use the r2SCAN meta-GGA functional. MP2020 energy corrections are PBE-specific and do not apply; `energy_corrected` equals `energy` for all rows.
+
+## Citation
+
+If you use this dataset, please cite the underlying databases:
+
+- **AFLOW**: Curtarolo et al., *Computational Materials Science* 58, 218–226 (2012)
+- **OQMD**: Saal et al., *JOM* 65, 1501–1509 (2013); Kirklin et al., *npj Computational Materials* 1, 15010 (2015)
+- **Materials Project**: Jain et al., *APL Materials* 1, 011002 (2013)
+- **Bader analysis**: Henkelman et al., *Computational Materials Science* 36, 354–360 (2006)
+- **r2SCAN functional**: Furness et al., *J. Phys. Chem. Lett.* 11, 8208–8215 (2020)