# Na–Si phases

> Na–Si system: 7 phases (tier A 4, liquid 1, needs_review 2); 5 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/NA-SI.html · Markdown: https://data.orchid-project.org/phases/pages/NA-SI.md

7 phases (tier A 4, liquid 1, needs_review 2); 5 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=NA-SI) · [full JSON](https://data.orchid-project.org/phases/systems/NA-SI.json) · [Na–Si system page](https://data.orchid-project.org/systems/NA-SI.html) · [Markdown](https://data.orchid-project.org/phases/pages/NA-SI.md) · [field reference](https://data.orchid-project.org/phases/SCHEMA.md)

Table: Phases of the Na–Si system (7)

| Phase | Structure | Basis | Stability (calculated) | Literature values | TDB models |
|---|---|---|---|---:|---:|
| [DIAMOND_A4](#phase-na-si-a4-diamond); _phase:na-si:a4-diamond_ | C (diamond) · A4 · cF8 · Fd-3m (227) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–2499.28 K, x(Si) 1–1 | 0 | 1 |
| [BCC_A2](#phase-na-si-bcc-a2); _phase:na-si:bcc-a2_ | W · A2 · cI2 · Im-3m (229) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–370.87 K, x(Si) 0–0 | 0 | 1 |
| [FCC_A1](#phase-na-si-fcc-a1); _phase:na-si:fcc-a1_ | Cu · A1 · cF4 · Fm-3m (225) | tier A: standard phase name | not stable in 1 calculated diagram(s) | 0 | 1 |
| [HCP_A3](#phase-na-si-hcp-a3); _phase:na-si: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-na-si-liquid); _phase:na-si:liquid_ | liquid | liquid | stable in 1 of 1 calculated diagram(s): 370.87–2500 K, x(Si) 0–1 | 0 | 1 |
| [NASI_HT](#phase-na-si-nasi-ht); _phase:na-si:nasi-ht_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 884.98–1071.77 K, x(Si) 0.5–0.5 | 0 | 1 |
| [NASI_LT](#phase-na-si-nasi-lt); _phase:na-si:nasi-lt_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 300–884.98 K, x(Si) 0.5–0.5 | 0 | 1 |

## DIAMOND_A4 (Na–Si)

- Id: `phase:na-si:a4-diamond`; status `assigned`
- Structure: C (diamond) · A4 · cF8 · Fd-3m (227); type `st:a4-c-diamond-cf8`; tier A: standard phase name; confidence high
- Stoichiometry: Si 1.0000
- Stability: stable in 1 of 1 calculated diagram(s): 300–2499.28 K, x(Si) 1–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:na-si:a4-diamond)

Names (2): _corpus: _corpus:phase:na-si:a4-diamond  
_tdb: _tdb:NaSi-12Hao.tdb:DIAMOND_A4  


### TDB models of DIAMOND_A4 (1): PHASE and CONSTITUENT statements as written

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): DIAMOND_A4, type code %, sha256 `fded76f9bf76e977…`

~~~~text
43: PHASE DIAMOND_A4 % 1 1 !
44: CONST DIAMOND_A4 : SI : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## BCC_A2 (Na–Si)

- Id: `phase:na-si: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): 300–370.87 K, x(Si) 0–0
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:na-si:bcc-a2)

Names (2): _corpus: _corpus:phase:na-si:bcc-a2  
_tdb: _tdb:NaSi-12Hao.tdb:BCC_A2  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): BCC_A2, type code %B, sha256 `fded76f9bf76e977…`

~~~~text
33: PHASE BCC_A2 %B 2 1 3 !
34: CONST BCC_A2 : NA% SI : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## FCC_A1 (Na–Si)

- Id: `phase:na-si:fcc-a1`; status `assigned`
- Structure: Cu · A1 · cF4 · Fm-3m (225); type `st:a1-cu-cf4`; 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:na-si:fcc-a1)

Names (2): _corpus: _corpus:phase:na-si:fcc-a1  
_tdb: _tdb:NaSi-12Hao.tdb:FCC_A1  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): FCC_A1, type code %A, sha256 `fded76f9bf76e977…`

~~~~text
28: PHASE FCC_A1 %A 2 1 1 !
29: CONST FCC_A1 : NA SI : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## HCP_A3 (Na–Si)

- Id: `phase:na-si: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:na-si:hcp-a3)

Names (2): _corpus: _corpus:phase:na-si:hcp-a3  
_tdb: _tdb:NaSi-12Hao.tdb:HCP_A3  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): HCP_A3, type code %A, sha256 `fded76f9bf76e977…`

~~~~text
38: PHASE HCP_A3 %A 2 1 0.5 !
39: CONST HCP_A3 : NA SI : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## LIQUID (Na–Si)

- Id: `phase:na-si:liquid`; status `assigned`
- Structure: liquid; type `st:liquid`; liquid; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 370.87–2500 K, x(Si) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:na-si:liquid)

Names (2): _corpus: _corpus:phase:na-si:liquid  
_tdb: _tdb:NaSi-12Hao.tdb:LIQUID  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): LIQUID, type code %, sha256 `fded76f9bf76e977…`

~~~~text
23: PHASE LIQUID:L % 1 1 !
24: CONST LIQUID:L : NA SI : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## NASI_HT (Na–Si)

- Id: `phase:na-si:nasi-ht`; status `needs_review`
- No structure assigned. Why: no_structure_token; polymorph_family:other phases of this system have the same composition
- Candidate (dft_oqmd): C2/c (15) — on-hull OQMD Na1 Si1 at x(SI)=0.5000
- Candidate (sgte_mmc2): (NaSi-ht) — Hallstedt 2025 mmc2 row for NASI_HT: NaSi-ht
- Stoichiometry: Na 0.5000, Si 0.5000
- Stability: stable in 1 of 1 calculated diagram(s): 884.98–1071.77 K, x(Si) 0.5–0.5
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:na-si:nasi-ht)

Names (2): _corpus: _corpus:phase:na-si:nasi-ht  
_tdb: _tdb:NaSi-12Hao.tdb:NASI_HT  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): NASI_HT, type code %, sha256 `fded76f9bf76e977…`

~~~~text
53: PHASE NASI_HT % 2 1 1 !
54: CONST NASI_HT : NA : SI : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## NASI_LT (Na–Si)

- Id: `phase:na-si:nasi-lt`; status `needs_review`
- No structure assigned. Why: no_structure_token; polymorph_family:other phases of this system have the same composition
- Candidate (dft_oqmd): C2/c (15) — on-hull OQMD Na1 Si1 at x(SI)=0.5000
- Candidate (sgte_mmc2): NaSi-lt · mC32 · C2/c (15) — Hallstedt 2025 mmc2 row for NASI_LT: NaSi-lt
- Candidate (tdb_comment): NaSi-lt · mC32 · C2/c, 15 — NaSi-12Hao.tdb: 'Prototype NaSi-lt (mC32, C2/c, 15)'
- Stoichiometry: Na 0.5000, Si 0.5000
- Stability: stable in 1 of 1 calculated diagram(s): 300–884.98 K, x(Si) 0.5–0.5
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:na-si:nasi-lt)

Names (2): _corpus: _corpus:phase:na-si:nasi-lt  
_tdb: _tdb:NaSi-12Hao.tdb:NASI_LT  


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

[NaSi-12Hao.tdb](https://orchid-project.org/data/databases/sgte-binary/NaSi-12Hao.tdb): NASI_LT, type code %, sha256 `fded76f9bf76e977…`

~~~~text
48: PHASE NASI_LT % 2 1 1 !
49: CONST NASI_LT : NA : SI : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.2298/JMMB120113024H](https://doi.org/10.2298/JMMB120113024H) D. Hao, M. Bu, Y. Wang, Y. Tang, Q. Gao, M. Wang, B. Hu, Y. Du, J. Mining Metall. B, 48, 273-82(2012).  
_assessment that models this phase_

## 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).