# O–Si system

> O–Si system: 36 accepted literature values (crystal structure 31, invariant reaction 3, other property 2) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

HTML: https://data.orchid-project.org/systems/O-SI.html · Markdown: https://data.orchid-project.org/systems/O-SI.md

36 accepted literature values from 3 paper(s) (model 2, DFT 3, unspecified 31); 0 calculated phase diagram(s). 9 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: [JSON](https://data.orchid-project.org/literature/systems/O-SI.json) · [CSV](https://data.orchid-project.org/systems/O-SI.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#O-SI) · [phases (17)](https://data.orchid-project.org/phases/pages/O-SI.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/O-SI.html) · [Markdown](https://data.orchid-project.org/systems/O-SI.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| model | 2 |
| DFT | 3 |
| unspecified | 31 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 3 |
| crystal structure | 31 |
| other property | 2 |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/O/O-SI.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/O/O-SI.json) · [CALPHAD hull SiO-92Hal](https://data.orchid-project.org/hulls/calphad-sgte/O/O-SI--SiO-92Hal.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the O–Si system (3)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 2130 | Gas -> L1 + L2 | Gas: O 0.5; L1: O 4.100e-4; L2: O 0.66662 | unspecified | [1] Hallstedt 1992 | Table 3, p. 9, row 3; `ORC-2IXLMG7XG3` |  |
| 1994 | monotectic: L2 -> L1 + Cristobalite | L2: O 0.66664; L1: O 2.600e-4; Cristobalite: O 0.66667 | unspecified | [1] Hallstedt 1992 | Table 3, p. 9, row 2; `ORC-2UFHNJ6YDQ` |  |
| 1687 | eutectic: L1 -> (Si) + Tridymite | L1: O 6.300e-5; (Si): O 4.500e-5; Tridymite: O 0.66667 | unspecified | [1] Hallstedt 1992 | Table 3, p. 9, row 1; `ORC-T3KP3KSB2O` |  |

## Other properties

### Crystal structure (31)

Table: Crystal structure, O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a | 5.007 Å | 0 | Quartz (SiO2); _alloy: O 0.666667, Si 0.333333_ | DFT | [2] Shin 2006 | Table 1, p. 3, row 7; `ORC-O2GEERKZE3.41ca9c` |  |
| Lattice a | 2.561 Å | 298.15 | SiO2(Fe2N-type); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 14; `ORC-5QWYWQHHEL.6a8464` |  |
| Lattice a | 4.9877 Å | 298.15 | SiO2(low cristobalite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 8; `ORC-BMKIZ2S2RG.f3e72c` |  |
| Lattice a | 4.957 Å | 298.15 | SiO2(low cristobalite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 7; `ORC-FECEURG3UR.ed5844` |  |
| Lattice a | 9.94 Å | 386 (\<) | SiO2(tridymite M-I); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 4; `ORC-JL3P54UTCP.404244` |  |
| Lattice a | 5.046 Å | 470.5 | SiO2(tridymite S-IV); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 1; `ORC-DVHGZGN7X2.29cb8d` |  |
| Lattice a | 5.052 Å | 470.5 | SiO2(tridymite S-IV); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 1; `ORC-DVHGZGN7X2.95185a` |  |
| Lattice a | 7.464 Å | 765.5 | SiO2 I (keatite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 9; `ORC-KBEVUQMXPZ.027df5` |  |
| Lattice a | 7.098 Å | 838 | SiO2 II (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 10; `ORC-KCKE3EVEX5.b96686` |  |
| Lattice a | 4.176 Å | 885.5 | SiO2 III (stishovite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 12; `ORC-HLN6FSA46S.facf0b` |  |
| Lattice a | 7.137 Å | 1273 (\<) | SiO2 IIb (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 11; `ORC-PFGFHT2DJI.4fde81` |  |
| Lattice a | 4.72 Å | 1368 | SiO2 (silica W); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 13; `ORC-KWIRTC252M.908c85` |  |
| Lattice b | 5.007 Å | 0 | Quartz (SiO2); _alloy: O 0.666667, Si 0.333333_ | DFT | [2] Shin 2006 | Table 1, p. 3, row 7; `ORC-O2GEERKZE3.95fb7b` |  |
| Lattice b | 17.21 Å | 386 (\<) | SiO2(tridymite M-I); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 4; `ORC-JL3P54UTCP.ac22de` |  |
| Lattice b | 12.334 Å | 838 | SiO2 II (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 10; `ORC-KCKE3EVEX5.f856ec` |  |
| Lattice b | 12.37 Å | 1273 (\<) | SiO2 IIb (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 11; `ORC-PFGFHT2DJI.2ba50a` |  |
| Lattice b | 5.16 Å | 1368 | SiO2 (silica W); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 13; `ORC-KWIRTC252M.d09bdd` |  |
| Lattice c | 5.496 Å | 0 | Quartz (SiO2); _alloy: O 0.666667, Si 0.333333_ | DFT | [2] Shin 2006 | Table 1, p. 3, row 7; `ORC-O2GEERKZE3.63dca5` |  |
| Lattice c | 4.112 Å | 298.15 | SiO2(Fe2N-type); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 14; `ORC-5QWYWQHHEL.313a01` |  |
| Lattice c | 6.9679 Å | 298.15 | SiO2(low cristobalite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 8; `ORC-BMKIZ2S2RG.ed21d8` |  |
| Lattice c | 6.8903 Å | 298.15 | SiO2(low cristobalite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 7; `ORC-FECEURG3UR.3c71e4` |  |
| Lattice c | 10.92 Å | 386 (\<) | SiO2(tridymite M-I); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 4; `ORC-JL3P54UTCP.60ede1` |  |
| Lattice c | 8.27 Å | 470.5 | SiO2(tridymite S-IV); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 1; `ORC-DVHGZGN7X2.11559a` |  |
| Lattice c | 8.236 Å | 470.5 | SiO2(tridymite S-IV); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 1; `ORC-DVHGZGN7X2.206537` |  |
| Lattice c | 8.62 Å | 765.5 | SiO2 I (keatite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 9; `ORC-KBEVUQMXPZ.2674bb` |  |
| Lattice c | 7.148 Å | 838 | SiO2 II (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 10; `ORC-KCKE3EVEX5.616a0b` |  |
| Lattice c | 2.666 Å | 885.5 | SiO2 III (stishovite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 12; `ORC-HLN6FSA46S.f15eff` |  |
| Lattice c | 7.174 Å | 1273 (\<) | SiO2 IIb (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 11; `ORC-PFGFHT2DJI.8bcb2f` |  |
| Lattice c | 8.36 Å | 1368 | SiO2 (silica W); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 13; `ORC-KWIRTC252M.3af4e7` |  |
| lattice beta | 120.33 ° |  | SiO2 IIb (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 11; `ORC-PFGFHT2DJI.4b2d7d` |  |
| lattice beta | 120.1 ° | 838 | SiO2 II (coesite); _alloy: Si 0.333333_ | unspecified | [3] Schnurre 2004 | Table 1, p. 5, row 10; `ORC-KCKE3EVEX5.f0d856` |  |

### Other property (2)

Table: Other property, O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Other; _printed: P_ | 11 mbar | 1689 | SiO2 (L) | model | [3] Schnurre 2004 | p. 19; `ORC-UFBWSNZ7GC.2e7d7d` | “At constant 11 mbar total pressure this shift is from 1693 K (stable) to 1689 K (metastable, with SiO2 (L)).” |
| Other; _printed: P_ | 11 mbar | 1693 |  | model | [3] Schnurre 2004 | p. 19; `ORC-UFBWSNZ7GC.25cc4d` | “At constant 11 mbar total pressure this shift is from 1693 K (stable) to 1689 K (metastable, with SiO2 (L)).” |

## Sources

Reporting papers the values were read from (a value cited from another work names that work in its row).

1. Bengt Hallstedt, Thermodynamic assessment of the Silicon — Oxygen system, Calphad 16, 53-61 (1992). [doi:10.1016/0364-5916(92)90038-y](https://doi.org/10.1016/0364-5916%2892%2990038-y)
2. Dongwon Shin, Raymundo Arróyave, Zi-Kui Liu, Thermodynamic modeling of the Hf–Si–O system, Calphad 30, 375-386 (2006). [doi:10.1016/j.calphad.2006.08.006](https://doi.org/10.1016/j.calphad.2006.08.006)
3. S.M. Schnurre, J. Gröbner, R. Schmid-Fetzer, Thermodynamics and phase stability in the Si–O system, Journal of Non-Crystalline Solids 336, 1-25 (2004). [doi:10.1016/j.jnoncrysol.2003.12.057](https://doi.org/10.1016/j.jnoncrysol.2003.12.057)

## Please cite

- R. Arróyave, J. Saal, D. Shin, ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23735569
- R. Arróyave, J. Saal, D. Shin, ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD) (version 2026.10), Zenodo (2026). https://doi.org/10.5281/zenodo.23735891
- 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 the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work); 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); 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.

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_literature_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735569},
  url       = {https://doi.org/10.5281/zenodo.23735569},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_hulls_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD)}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735891},
  url       = {https://doi.org/10.5281/zenodo.23735891}
}

@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 ORCHID ([CITATION.cff](https://data.orchid-project.org/CITATION.cff)) and the original sources. Quotes are short excerpts kept so that each value can be checked; they remain under the publishers' copyright and are not relicensed. Source papers, page images and full text are not redistributed. Field reference: [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt). Found an error? The report link of a value (Markdown: its id, ORC-..., in the Location column) opens a pre-filled GitHub issue, https://github.com/orchid-calphad/orchid-data/issues/new?template=report-value-error.yml&record_id=\<id>, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).