# Np–Pu phases

> Np–Pu system: 11 phases (tier A 6, liquid 1, needs_review 4); 10 stable in a calculated diagram in the ORCHID phase registry, with names, structure type when the stored evidence supports an assignment under the stated tier rules, calculated stability, verbatim TDB PHASE/CONSTITUENT statements and example references.

HTML: https://data.orchid-project.org/phases/pages/NP-PU.html · Markdown: https://data.orchid-project.org/phases/pages/NP-PU.md

11 phases (tier A 6, liquid 1, needs_review 4); 10 stable in a calculated diagram. Structure types are assigned only when the stored evidence supports an assignment under the stated tier rules (tier A: standard phase name; tier B: unique Materials Project + OQMD on-hull match, DFT-supported; tier C: one structure stated by the assessment's crystallographic table, assessor-stated); other phases list candidates and are marked needs_review. Stability is from phase diagrams calculated with pycalphad from the SGTE binary collection (evidence class: model).

Data: [interactive registry](https://orchid-project.org/phases/?q=NP-PU) · [full JSON](https://data.orchid-project.org/phases/systems/NP-PU.json) · [Np–Pu system page](https://data.orchid-project.org/systems/NP-PU.html) · [Markdown](https://data.orchid-project.org/phases/pages/NP-PU.md) · [field reference](https://data.orchid-project.org/phases/SCHEMA.md)

Table: Phases of the Np–Pu system (11)

| Phase | Structure | Basis | Stability (calculated) | Literature values | TDB models |
|---|---|---|---|---:|---:|
| [TETRAGONAL_A6](#phase-np-pu-a6-tetragonal); _phase:np-pu:a6-tetragonal_ | In · A6 · tI2 · I4/mmm (139) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 700.79–764.96 K, x(Pu) 0.94627–1 | 0 | 1 |
| [TETRAG_AD](#phase-np-pu-ad-tetrag); _phase:np-pu:ad-tetrag_ | beta-Np · A_d · tP4 · P4/nmm (129) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 549.1–855.55 K, x(Pu) 0–0.20886 | 0 | 1 |
| [BCC_A2](#phase-np-pu-bcc-a2); _phase:np-pu:bcc-a2_ | W · A2 · cI2 · Im-3m (229) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 709.96–913 K, x(Pu) 0–1 | 0 | 1 |
| [FCC_A1](#phase-np-pu-fcc-a1); _phase:np-pu:fcc-a1_ | Cu · A1 · cF4 · Fm-3m (225) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 593.44–829.9 K, x(Pu) 0.95063–1 | 0 | 1 |
| [HCP_A3](#phase-np-pu-hcp-a3); _phase:np-pu:hcp-a3_ | Mg · A3 · hP2 · P6_3/mmc (194) | tier A: standard phase name | not stable in 1 calculated diagram(s) | 0 | 1 |
| [LIQUID](#phase-np-pu-liquid); _phase:np-pu:liquid_ | liquid | liquid | stable in 1 of 1 calculated diagram(s): 831.62–4000 K, x(Pu) 0–1 | 0 | 1 |
| [NPPU_ETA](#phase-np-pu-nppu-eta); _phase:np-pu:nppu-eta_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 554.55–776.31 K, x(Pu) 0.52046–0.97329 | 0 | 1 |
| [ORTHO_AC](#phase-np-pu-ortho-ac); _phase:np-pu:ortho-ac_ | alpha-Np · A_c · oP8 · Pnma (62) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–555.02 K, x(Pu) 0–0.05172 | 0 | 1 |
| [ALPHA_PU](#phase-np-pu-pu-alpha); _phase:np-pu:pu-alpha_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 300–572.02 K, x(Pu) 0.08645–1 | 0 | 1 |
| [BETA_PU](#phase-np-pu-pu-beta); _phase:np-pu:pu-beta_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 397.62–820.42 K, x(Pu) 0.20885–1 | 0 | 1 |
| [GAMMA_PU](#phase-np-pu-pu-gamma); _phase:np-pu:pu-gamma_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 402.91–599.83 K, x(Pu) 0.98334–1 | 0 | 1 |

## TETRAGONAL_A6 (Np–Pu)

- Id: `phase:np-pu:a6-tetragonal`; status `assigned`
- Structure: In · A6 · tI2 · I4/mmm (139); type `st:a6-in-ti2`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 700.79–764.96 K, x(Pu) 0.94627–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:a6-tetragonal)

Names (2): _corpus: _corpus:phase:np-pu:a6-tetragonal  
_tdb: _tdb:NpPu-10Kur.tdb:TETRAGONAL_A6  


### TDB models of TETRAGONAL_A6 (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): TETRAGONAL_A6, type code %, sha256 `4debc868e0be8e01…`

~~~~text
42: PHASE TETRAGONAL_A6 % 1 1 !
43: CONST TETRAGONAL_A6 : NP PU% : !
~~~~

## TETRAG_AD (Np–Pu)

- Id: `phase:np-pu:ad-tetrag`; status `assigned`
- Structure: beta-Np · A_d · tP4 · P4/nmm (129); type `st:a-d-beta-np-tp4`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 549.1–855.55 K, x(Pu) 0–0.20886
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:ad-tetrag)

Names (2): _corpus: _corpus:phase:np-pu:ad-tetrag  
_tdb: _tdb:NpPu-10Kur.tdb:TETRAG_AD  


### TDB models of TETRAG_AD (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): TETRAG_AD, type code %, sha256 `4debc868e0be8e01…`

~~~~text
52: PHASE TETRAG_AD % 1 1 !
53: CONST TETRAG_AD : NP% PU : !
~~~~

## BCC_A2 (Np–Pu)

- Id: `phase:np-pu:bcc-a2`; status `assigned`
- Structure: W · A2 · cI2 · Im-3m (229); type `st:a2-w-ci2`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 709.96–913 K, x(Pu) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:bcc-a2)

Names (2): _corpus: _corpus:phase:np-pu:bcc-a2  
_tdb: _tdb:NpPu-10Kur.tdb:BCC_A2  


### TDB models of BCC_A2 (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): BCC_A2, type code %B, sha256 `4debc868e0be8e01…`

~~~~text
32: PHASE BCC_A2 %B 2 1 3 !
33: CONST BCC_A2 : NP% PU% : VA : !
~~~~

## FCC_A1 (Np–Pu)

- Id: `phase:np-pu:fcc-a1`; status `assigned`
- Structure: Cu · A1 · cF4 · Fm-3m (225); type `st:a1-cu-cf4`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 593.44–829.9 K, x(Pu) 0.95063–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:fcc-a1)

Names (2): _corpus: _corpus:phase:np-pu:fcc-a1  
_tdb: _tdb:NpPu-10Kur.tdb:FCC_A1  


### TDB models of FCC_A1 (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): FCC_A1, type code %A, sha256 `4debc868e0be8e01…`

~~~~text
27: PHASE FCC_A1 %A 2 1 1 !
28: CONST FCC_A1 : NP PU% : VA : !
~~~~

## HCP_A3 (Np–Pu)

- Id: `phase:np-pu:hcp-a3`; status `assigned`
- Structure: Mg · A3 · hP2 · P6_3/mmc (194); type `st:a3-mg-hp2`; tier A: standard phase name; confidence high
- Stability: not stable in 1 calculated diagram(s)
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:hcp-a3)

Names (2): _corpus: _corpus:phase:np-pu:hcp-a3  
_tdb: _tdb:NpPu-10Kur.tdb:HCP_A3  


### TDB models of HCP_A3 (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): HCP_A3, type code %A, sha256 `4debc868e0be8e01…`

~~~~text
37: PHASE HCP_A3 %A 2 1 0.5 !
38: CONST HCP_A3 : NP PU : VA : !
~~~~

## LIQUID (Np–Pu)

- Id: `phase:np-pu:liquid`; status `assigned`
- Structure: liquid; type `st:liquid`; liquid; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 831.62–4000 K, x(Pu) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:liquid)

Names (2): _corpus: _corpus:phase:np-pu:liquid  
_tdb: _tdb:NpPu-10Kur.tdb:LIQUID  


### TDB models of LIQUID (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): LIQUID, type code %, sha256 `4debc868e0be8e01…`

~~~~text
22: PHASE LIQUID:L % 1 1 !
23: CONST LIQUID:L : NP PU : !
~~~~

## NPPU_ETA (Np–Pu)

- Id: `phase:np-pu:nppu-eta`; status `needs_review`
- No structure assigned. Why: no_structure_token; off_stoichiometric_model
- Candidate (sgte_mmc2): (NpPu-eta) · tP52 — Hallstedt 2025 mmc2 row for NPPU_ETA: NpPu-eta
- Stability: stable in 1 of 1 calculated diagram(s): 554.55–776.31 K, x(Pu) 0.52046–0.97329
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:nppu-eta)

Names (2): _corpus: _corpus:phase:np-pu:nppu-eta  
_tdb: _tdb:NpPu-10Kur.tdb:NPPU_ETA  


### TDB models of NPPU_ETA (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): NPPU_ETA, type code %, sha256 `4debc868e0be8e01…`

~~~~text
72: PHASE NPPU_ETA % 1 1 !
73: CONST NPPU_ETA : NP PU : !
~~~~

## ORTHO_AC (Np–Pu)

- Id: `phase:np-pu:ortho-ac`; status `assigned`
- Structure: alpha-Np · A_c · oP8 · Pnma (62); type `st:a-c-alpha-np-op8`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 300–555.02 K, x(Pu) 0–0.05172
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:ortho-ac)

Names (2): _corpus: _corpus:phase:np-pu:ortho-ac  
_tdb: _tdb:NpPu-10Kur.tdb:ORTHO_AC  


### TDB models of ORTHO_AC (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): ORTHO_AC, type code %, sha256 `4debc868e0be8e01…`

~~~~text
47: PHASE ORTHO_AC % 1 1 !
48: CONST ORTHO_AC : NP% PU : !
~~~~

## ALPHA_PU (Np–Pu)

- Id: `phase:np-pu:pu-alpha`; status `needs_review`
- No structure assigned. Why: no_structure_token; off_stoichiometric_model
- Candidate (sgte_mmc2): alpha-Pu · mP16 · P2_1/m (11) — Hallstedt 2025 mmc2 row for ALPHA_PU: Pu (alpha)
- Candidate (tdb_comment): alpha-Pu · mP16 · P2_1/m — NpPu-10Kur.tdb: 'Prototype alpha-Pu (mP16, P2_1/m)'
- Stability: stable in 1 of 1 calculated diagram(s): 300–572.02 K, x(Pu) 0.08645–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:pu-alpha)

Names (2): _corpus: _corpus:phase:np-pu:pu-alpha  
_tdb: _tdb:NpPu-10Kur.tdb:ALPHA_PU  


### TDB models of ALPHA_PU (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): ALPHA_PU, type code %, sha256 `4debc868e0be8e01…`

~~~~text
57: PHASE ALPHA_PU % 1 1 !
58: CONST ALPHA_PU : NP PU% : !
~~~~

## BETA_PU (Np–Pu)

- Id: `phase:np-pu:pu-beta`; status `needs_review`
- No structure assigned. Why: no_structure_token; off_stoichiometric_model
- Candidate (sgte_mmc2): beta-Pu · mC34 · C2/m (12) — Hallstedt 2025 mmc2 row for BETA_PU: Pu (beta)
- Candidate (tdb_comment): beta-Pu · mC34 · C2/m — NpPu-10Kur.tdb: 'Prototype beta-Pu (mC34, C2/m)'
- Stability: stable in 1 of 1 calculated diagram(s): 397.62–820.42 K, x(Pu) 0.20885–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:pu-beta)

Names (2): _corpus: _corpus:phase:np-pu:pu-beta  
_tdb: _tdb:NpPu-10Kur.tdb:BETA_PU  


### TDB models of BETA_PU (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): BETA_PU, type code %, sha256 `4debc868e0be8e01…`

~~~~text
62: PHASE BETA_PU % 1 1 !
63: CONST BETA_PU : NP PU% : !
~~~~

## GAMMA_PU (Np–Pu)

- Id: `phase:np-pu:pu-gamma`; status `needs_review`
- No structure assigned. Why: no_structure_token; off_stoichiometric_model
- Candidate (sgte_mmc2): gamma-Pu · oF8 · Fddd (70) — Hallstedt 2025 mmc2 row for GAMMA_PU: Hg4In, Pu (gamma)
- Candidate (tdb_comment): gamma-Pu · oF8 · Fddd — NpPu-10Kur.tdb: 'Prototype gamma-Pu (oF8, Fddd)'
- Stability: stable in 1 of 1 calculated diagram(s): 402.91–599.83 K, x(Pu) 0.98334–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:np-pu:pu-gamma)

Names (2): _corpus: _corpus:phase:np-pu:pu-gamma  
_tdb: _tdb:NpPu-10Kur.tdb:GAMMA_PU  


### TDB models of GAMMA_PU (1): PHASE and CONSTITUENT statements as written

[NpPu-10Kur.tdb](https://orchid-project.org/data/databases/sgte-binary/NpPu-10Kur.tdb): GAMMA_PU, type code %, sha256 `4debc868e0be8e01…`

~~~~text
67: PHASE GAMMA_PU % 1 1 !
68: CONST GAMMA_PU : NP PU% : !
~~~~

## Please cite

- R. Arróyave, J. Saal, D. Shin, ORCHID-Registry: phase registry of binary systems (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23735970
- R. Arróyave, J. Saal, D. Shin, ORCHID data: umbrella record of the ORCHID datasets (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23736065

Also cite B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, https://doi.org/10.1016/j.calphad.2025.102833 (CC BY 4.0), and the original assessment named in each file; A. Jain et al., The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002, https://doi.org/10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501, https://doi.org/10.1007/s11837-013-0755-4 and S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010, https://doi.org/10.1038/npjcompumats.2015.10 (CC BY 4.0); the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work).

Version 1, machine-extracted: values were read by language-model readers constrained to quote their source and checked automatically, and the release was then audited on the printed pages by adversarial audits, an independent second review of fit-facing records and a preliminary human review of a frozen sample. Flags such as accepted and ESPEI-ready record screening results, not certification; known issues are listed in the release notes.

```bibtex
@misc{orchid_phase_registry_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Registry: phase registry of binary systems}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735970},
  url       = {https://doi.org/10.5281/zenodo.23735970},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_data_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID data: umbrella record of the ORCHID datasets}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23736065},
  url       = {https://doi.org/10.5281/zenodo.23736065},
  note      = {Version 1, machine-extracted}
}
```

---

Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite the ORCHID phase registry and the sources named on the page (TDB assessments, Hallstedt 2025, Materials Project, OQMD). TDB statements are quoted as written; parameter expressions are not reproduced. Field reference: [SCHEMA.md](https://data.orchid-project.org/phases/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt).