# Ge–O system

> Ge–O system: 30 accepted literature values (formation 14, heat capacity / entropy / enthalpy 9, phase transition 4, invariant reaction 2) and 2 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

30 accepted literature values from 1 paper(s) (experimental 18, model 9, unspecified 3); 2 calculated phase diagram(s). 8 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/GE-O.json) · [CSV](https://data.orchid-project.org/systems/GE-O.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#GE-O) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#GE-O/GeO-15Din.json) · [phases (10)](https://data.orchid-project.org/phases/pages/GE-O.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/GE-O.html) · [Markdown](https://data.orchid-project.org/systems/GE-O.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 18 |
| model | 9 |
| unspecified | 3 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 2 |
| phase transition | 4 |
| formation | 14 |
| heat capacity / entropy / enthalpy | 9 |
| other property | 1 |

## Calculated phase diagrams

Binary phase diagrams calculated with pycalphad 0.11.2 from the SGTE binary collection (Hallstedt 2025, CC BY 4.0). Evidence class: model.

Table: Assessments with a calculated phase diagram

| TDB file | Assessment | SHA-256 | Links |
|---|---|---|---|
| GeO-15Din.tdb | A.T. Dinsdale, A. Akhmetova, A.V. Khvan, N. Aristova, J. Phase Equilib. Diffus., 36, 254-61(2015). [doi:10.1007/s11669-015-0379-1](https://doi.org/10.1007/s11669-015-0379-1) | `004d6c7cf629014a386794c6bee28f4648f67db68a6637c066d4e70afa63d0ed` | [viewer](https://orchid-project.org/phase-diagrams/#GE-O/GeO-15Din.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/GeO-15Din.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/GeO-15Din.json) |
| GeO-21Baj-3g.tdb | I. Bajenova, A. Khvan, M. Derevyanko, N. Aristova, A. Dinsdale, A. Kondriatev, A. Pisch, Calphad, 74, 102299(2021). [doi:10.1016/j.calphad.2021.102299](https://doi.org/10.1016/j.calphad.2021.102299) | `904325ae56bbb509f886d3d920b843a6c2e15e9e530a7f6f10c32ab793adce67` | [viewer](https://orchid-project.org/phase-diagrams/#GE-O/GeO-21Baj-3g.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/GeO-21Baj-3g.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/GeO-21Baj-3g.json) |

Table: Calculated three-phase invariants (model, mole fraction of the second component)

| TDB file | T (K) | Phases at the invariant |
|---|---:|---|
| GeO-15Din.tdb | 1207.81 | DIAMOND_A4 (x(O) 0) + ION#2 (x(O) 0.0117) + ION (x(O) 0.57976) |
| GeO-21Baj-3g.tdb | 1389.19 | GEO2_HT (x(O) 0.66667) + ION (x(O) 0.66667) + GAS (x(O) 1) |
| GeO-21Baj-3g.tdb | 1207.81 | DIAMOND_A4 (x(O) 0) + ION#2 (x(O) 0.0117) + ION (x(O) 0.57976) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/GE/GE-O.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/GE/GE-O.json) · [CALPHAD hull GeO-15Din](https://data.orchid-project.org/hulls/calphad-sgte/GE/GE-O--GeO-15Din.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Ge–O system (2)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 1185 | eutectic |  | experimental | [1] Dinsdale 2015 | p. 1; `ORC-I7ARXPVH4Y` | “Measurements carried out by Trumbore et al. indicate that the stable eutectic involving the lower temperature tetragonal phase should be at 1185 K.” |
| 1143 | eutectic |  | experimental | [1] Dinsdale 2015; _cites Candidus 1955_ [doi](https://doi.org/10.1063/1.1742038) | p. 1; `ORC-DLJY5KG6WD` | “Candidus and Tuomi\[29\] measured the eutectic temperature involving crystalline Ge and GeO2 to be 1143 K.” |

## Formation enthalpies

Literature values in kJ/mol-atom where the per-atom basis is known. DFT columns: the lowest-energy entry at the same composition (Materials Project 2026.04.13, OQMD v1.8; different energy references, never averaged), from [dft_parity.json](https://data.orchid-project.org/literature/dft_parity.json).

Table: Enthalpies of formation, Ge–O system (14)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| GeO2 hexagonal |  | -574 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Katayama 1975_ | Table 4, p. 4, row 10; `ORC-K3J25RITDO.965b00` |  |
| GeO2 hexagonal |  | -556.5 kJ/mol (basis unstated) ± 2 | 298.15 | model |  |  | [1] Dinsdale 2015; _cites Faktor 1965_ [doi](https://doi.org/10.1149/1.2423702) | Table 4, p. 4, row 8; `ORC-3JBOBH5KCF` |  |
| GeO2 hexagonal |  | -556.1 kJ/mol (basis unstated) ± 2 | 298.15 | model |  |  | [1] Dinsdale 2015 | Table 4, p. 4, row 14; `ORC-TKE4BRTWCG` |  |
| GeO2 hexagonal |  | -556 kJ/mol (basis unstated) ± 8 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Jolly 1952_ [doi](https://doi.org/10.1021/ja01142a056) | Table 4, p. 4, row 3; `ORC-2DQC5PPW4J` |  |
| GeO2 hexagonal |  | -556 kJ/mol (basis unstated) ± 5 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Yokokawa 1957_ [doi](https://doi.org/10.1021/ja01570a016) | Table 4, p. 4, row 4; `ORC-M4ZCOTCL47` |  |
| GeO2 hexagonal |  | -555.4 kJ/mol (basis unstated) ± 2 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Yokokawa 1957_ [doi](https://doi.org/10.1021/ja01570a016) | Table 4, p. 4, row 5; `ORC-YPMXD3NAJT` |  |
| GeO2 hexagonal |  | -554.7 kJ/mol (basis unstated) ± 1 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Gross 1966_ [doi](https://doi.org/10.1039/tf9666202388) | Table 4, p. 4, row 9; `ORC-23NHBNQJKD` |  |
| GeO2 hexagonal |  | -554.7 kJ/mol (basis unstated) ± 1 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Katayama 1975_ | Table 4, p. 4, row 11; `ORC-65NC2C3TQ2` |  |
| GeO2 hexagonal |  | -554.7 kJ/mol (basis unstated) ± 1 | 298.15 | model |  |  | [1] Dinsdale 2015; _cites Gurvich 1990_ | Table 4, p. 4, row 12; `ORC-WQ2XBV4SWA` |  |
| GeO2 hexagonal |  | -553.82 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Dinsdale 2015; _cites Richet 1990_ [doi](https://doi.org/10.1007/bf00209228) | Table 4, p. 4, row 13; `ORC-TZURBNFNPE.a7e5a7` |  |
| GeO2 hexagonal |  | -553 kJ/mol (basis unstated) ± 5 | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Bills 1964_ [doi](https://doi.org/10.1021/j100786a016) | Table 4, p. 4, row 7; `ORC-2P2GNLY7DI` |  |
| GeO2 hexagonal |  | -540.1 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Mah 1962_ | Table 4, p. 4, row 6; `ORC-HLGTCQNHJY.6898fe` |  |
| GeO2 hexagonal |  | -538 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Hahn 1940_ [doi](https://doi.org/10.1002/zaac.19402440203) | Table 4, p. 4, row 2; `ORC-AVC7326QWT.7158f1` |  |
| GeO2 hexagonal |  | -536 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Dinsdale 2015; _cites Becker 1932_ [doi](https://doi.org/10.1515/zpch-1932-16107) | Table 4, p. 4, row 1; `ORC-KPAQ7GA6CF.98dc8d` |  |

## Other properties

### Phase transition (4)

Table: Phase transition, Ge–O system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 1308 K | 1308 | polymorphic: tet → hex; _alloy: O 0.666667_ | unspecified | [1] Dinsdale 2015 | Table 6, p. 5, row 4; `ORC-4TD6B2YWIT` |  |
| Phase transition | 1342.3 K | 1342.3 | congruent transformation: tet → liq; _alloy: O 0.666667_ | unspecified | [1] Dinsdale 2015 | Table 6, p. 5, row 6; `ORC-3N7SVS4M2J` |  |
| Phase transition | 1359 K | 1359 | tetragonal GeO2 | experimental | [1] Dinsdale 2015; _cites Laubengayer 1932_ | p. 2; `ORC-7QT7U5B3PN.ef2de4` | “The metastable melting point of tetragonal GeO2 was reported to be 1359 ± 5 K by Laubengayer and Morton.\[8\]” |
| Phase transition | 1388 K | 1388 | congruent transformation: hex → liq; _alloy: O 0.666667_ | unspecified | [1] Dinsdale 2015 | Table 6, p. 5, row 5; `ORC-NDUBZG7RH3` |  |

### Heat capacity / entropy / enthalpy (9)

Table: Heat capacity / entropy / enthalpy, Ge–O system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: S298.15 (3rd law)_ | 57.279 J/mol (basis unstated)/K | 298.15 | hexagonal GeO2; _alloy: O 0.666667_ | model | [1] Dinsdale 2015 | Table 5, p. 4, row 2; `ORC-NCC4T6UT7P` |  |
| Entropy; _printed: S298.15 (3rd law)_ | 55.27 J/mol (basis unstated)/K ± 0.4 | 298.15 | hexagonal GeO2; _alloy: O 0.666667_ | experimental | [1] Dinsdale 2015; _cites King 1958_ [doi](https://doi.org/10.1021/ja01541a005) | Table 5, p. 4, row 1; `ORC-PP3LTVC7GN` |  |
| Entropy; _printed: S298.15_ | 40.58 unknown ± 2.9 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | model | [1] Dinsdale 2015; _cites Gurvich 1990_ | Table 2, p. 3, row 5; `ORC-EA3WTSAHXD` |  |
| Entropy; _printed: S298.15 (3rd law)_ | 32.4 unknown ± 1.6 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | experimental | [1] Dinsdale 2015; _cites Counsell 1967_ | Table 2, p. 3, row 4; `ORC-MR3VZIJUMN` |  |
| Entropy; _printed: S298.15_ | 39.71 unknown ± 0.1 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | model | [1] Dinsdale 2015; _cites Richet 1990_ [doi](https://doi.org/10.1007/bf00209228) | Table 2, p. 3, row 6; `ORC-MVIIVN7T2O` |  |
| Entropy; _printed: S298.15_ | 39.71 unknown ± 0.13 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | model | [1] Dinsdale 2015 | Table 2, p. 3, row 7; `ORC-P4NX2CSCNK` |  |
| Entropy; _printed: S298.15 (3rd law)_ | 39.3 unknown ± 1.6 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | experimental | [1] Dinsdale 2015; _cites Yu 1968_ | Table 2, p. 3, row 2; `ORC-PH2IV3RXZH` |  |
| Entropy; _printed: S298.15 (2nd law)_ | 36.2 unknown ± 12 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | model | [1] Dinsdale 2015; _cites Newns 1966_ | Table 2, p. 3, row 3; `ORC-SGJ2ZRJF3X` |  |
| Entropy; _printed: S298.15 (2nd law)_ | 31.1 unknown ± 10 | 298.15 | tetragonal GeO2; _alloy: O 0.666667_ | experimental | [1] Dinsdale 2015; _cites Faktor 1965_ [doi](https://doi.org/10.1149/1.2423702) | Table 2, p. 3, row 1; `ORC-T3UP7TNUMC` |  |

### Other property (1)

Table: Other property, Ge–O system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Other; _printed: enthalpy of fusion_ | 17.15 kJ/mol | 1388 |  | experimental | [1] Dinsdale 2015; _cites Newns 1966_ | p. 3; `ORC-J5JKGKIVE7` | “The enthalpy of fusion of the hexagonal form (17.15 kJ/mol) at the melting point (1388 K) has been obtained by Newns and Hanks\[11\] using a differential thermal analysis technique.” |

## Sources

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

1. A. T. Dinsdale, A. Akhmetova, A. V. Khvan, N. Aristova, A Critical Assessment of Thermodynamic and Phase Diagram Data for the Ge-O System, J. Phase Equilib. Diffus. 36, 254-261 (2015). [doi:10.1007/s11669-015-0379-1](https://doi.org/10.1007/s11669-015-0379-1)

## 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-Diagrams: calculated binary phase diagrams (version 2026.10), Zenodo (2026). https://doi.org/10.5281/zenodo.23735859
- 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); 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).

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_phase_diagrams_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Diagrams: calculated binary phase diagrams}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735859},
  url       = {https://doi.org/10.5281/zenodo.23735859}
}

@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/).