# Co system

> Co system: 26 accepted literature values (crystal structure 9, invariant reaction 8, formation 3, mixing / partial 3) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

26 accepted literature values from 12 paper(s) (experimental 7, model 13, DFT 4, unspecified 2); 0 calculated phase diagram(s).

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

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 7 |
| model | 13 |
| DFT | 4 |
| unspecified | 2 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 8 |
| phase transition | 2 |
| formation | 3 |
| mixing / partial | 3 |
| activity / EMF / Gibbs energy | 1 |
| crystal structure | 9 |

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Co system (8)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 1768 | congruent melting: Co(FCC) \<-> Co(L) | Co(FCC):  | unspecified | [1] Vassilev 2004; _cites Dinsdale 1991_ | Table 3, p. 6, row 1; `ORC-R7BQHCQXRN` |  |
| 695.15 | polymorphic: αCo ↔ εCo | εCo:  | experimental | [2] Liu 2008; _cites Okamoto 2000_ | Table 2, p. 4, row 21; `ORC-QOTTPZW2UI` |  |
| 695.15 | polymorphic: αCo -> εCo | εCo:  | model | [3] Ansara 1991 | Table 1, p. 5, row 13; `ORC-ZQAU5CDWTC` |  |
| 695 | polymorphic: (αCo) ↔ (εCo) |  | unspecified | [4] Zhang 2008; _cites Dudkin 1956_ | Table 1, p. 2, row 1; `ORC-EEMFXYMJ7D` |  |
| 695 | α-Co -> ε-Co | ε-Co:  | experimental | [5] Golumbfskie 2006; _cites Niessen 1983_ [doi](https://doi.org/10.1016/0364-5916%2883%2990030-5) | Table 2, p. 2, row 2; `ORC-EMQ3DPPOQH` |  |
| 695 | α-Co -> ε-Co | ε-Co:  | model | [5] Golumbfskie 2006 | Table 2, p. 2, row 1; `ORC-FZUF6VPZME` |  |
| 695 | polymorphic: (αCo) ↔ (εCo) |  | model | [4] Zhang 2008 | Table 1, p. 2, row 2; `ORC-ZVRN2RAGZM` |  |
| 694.15 | polymorphic: αCo ↔ εCo | εCo:  | model | [2] Liu 2008 | Table 2, p. 4, row 22; `ORC-PSBM5BXQU2` |  |

## 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, Co system (3)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| m-(Co,Fe)4Al13 |  | -40.44 kJ/mol-atom |  | DFT |  |  | [6] Ostrowska 2019; _cites Shevchenko 2014_ [doi](https://doi.org/10.1134/s003602441405029x) | Table 2, p. 2, row 6; `ORC-BOFTHCMKTY` |  |
| m-(Co,Fe)4Al13 |  | -37.64 kJ/mol-atom |  | DFT |  |  | [6] Ostrowska 2019; _cites AFLOW_ | Table 2, p. 2, row 7; `ORC-EPVZKAS77L` |  |
| m-(Co,Fe)4Al13 |  | -37.26 kJ/mol-atom |  | DFT |  |  | [6] Ostrowska 2019; _cites materialsproject_ | Table 2, p. 2, row 5; `ORC-AV6E53YJPK` |  |

## Other properties

### Phase transition (2)

Table: Phase transition, Co system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 695 K | 695 | ε-Co + α-Co | model | [7] Chen 2003; _cites Dinsdale 2003_ | p. 1; `ORC-FSFSFQONKY` | “␧-Co (hcp) is stable up to 695 K, at which temperature it transforms to ␣-Co (fcc) \[1991Din\].” |
| Phase transition | 1150 K | 1150 | magnetic | experimental | [8] Davydov 1999; _cites Takayama 1981_ [doi](https://doi.org/10.2320/matertrans1960.22.315) | p. 2; `ORC-34QIEUKH66` | “Using x-ray diffraction (XRD) and microprobe analysis, \[81Tak\] detected an abrupt change in the fcc (Co) solvus line at about 1150 K and showed that this anomaly is caused by the magnetic transformation in this phase.” |

### Mixing / partial (3)

Table: Mixing / partial, Co system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Enthalpy of mixing; _printed: ΔH^E_ | 0 kJ/mol (basis unstated) | 1810.15 | liquid; _alloy: Co 1_ | experimental | [9] Kubišta 2000 | Table 4, p. 4, row 1; `ORC-TR6KLBVTSD.76ad95` |  |
| Entropy of mixing; _printed: ΔS^E_ | 0 J/mol (basis unstated)/K | 1810.15 | liquid; _alloy: Co 1_ | experimental | [9] Kubišta 2000 | Table 4, p. 4, row 1; `ORC-TR6KLBVTSD.125cc1` |  |
| Gibbs energy of mixing; _printed: ΔG^E_ | 0 kJ/mol (basis unstated) | 1810.15 | liquid; _alloy: Co 1_ | experimental | [9] Kubišta 2000 | Table 4, p. 4, row 1; `ORC-TR6KLBVTSD.be92d6` |  |

### Activity / EMF / Gibbs energy (1)

Table: Activity / EMF / Gibbs energy, Co system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Gibbs energy; _printed: ΔG°_ | -98862 J/mol | 1873 | liquid Co | experimental | [7] Chen 2003; _cites Fischer 1971_ | Table 7, p. 11, row 4; `ORC-VUIL5KUVVB` |  |

### Crystal structure (9)

Table: Crystal structure, Co system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a | 3.545 Å |  | fcc; _alloy: Co 1_ | model | [10] Kim 2011 | Table 1, p. 2, row 3; `ORC-I5TFQPJBCT` |  |
| Lattice a | 3.518 Å |  | fcc; _alloy: Co 1_ | model | [10] Kim 2011 | Table 1, p. 2, row 2; `ORC-IPXVG7XUT6` |  |
| Lattice a | 3.501 Å |  | fcc; _alloy: Co 1_ | model | [10] Kim 2011 | Table 1, p. 2, row 1; `ORC-P5HVUCHT4Q` |  |
| Lattice a | 3.544 Å | 298.15 | αCo | model | [11] Cacciamani 2000; _cites Villars 1991_ | Table 1, p. 2, row 2; `ORC-UVEFPHPMDC` |  |
| Lattice a | 2.507 Å | 298.15 | εCo | model | [11] Cacciamani 2000; _cites Villars 1991_ | Table 1, p. 2, row 1; `ORC-JG7PSBO7MK.148621` |  |
| Lattice a | 2.505 Å | 298.15 | εCo | model | [11] Cacciamani 2000; _cites Villars 1991_ | Table 1, p. 2, row 1; `ORC-JG7PSBO7MK.3eae46` |  |
| Lattice c | 4.089 Å | 298.15 | εCo | model | [11] Cacciamani 2000; _cites Villars 1991_ | Table 1, p. 2, row 1; `ORC-JG7PSBO7MK.36df5f` |  |
| Lattice c | 4.07 Å | 298.15 | εCo | model | [11] Cacciamani 2000; _cites Villars 1991_ | Table 1, p. 2, row 1; `ORC-JG7PSBO7MK.eac3cf` |  |
| Molar volume; _printed: V0_ | 10.82 Å3/atom | 0 | hcp(Co) | DFT | [12] Zhou 2020 | Table V, p. 12, row 1; `ORC-RSFI3WEZR3` |  |

## Sources

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

1. George Penev Vassilev, Min Jiang, Thermodynamic Optimization of the Co-Zn System, Journal of Phase Equilibria &amp; Diffusion 25, 259-268 (2004). [doi:10.1361/15477030419522](https://doi.org/10.1361/15477030419522)
2. X.J. Liu, P. Yu, C.P. Wang, K. Ishida, Thermodynamic evaluation of the Co–Sc and Fe–Sc systems, Journal of Alloys and Compounds 466, 169-175 (2008). [doi:10.1016/j.jallcom.2007.11.069](https://doi.org/10.1016/j.jallcom.2007.11.069)
3. I Ansara, F Ajersch, The Ga-Pb (Gallium-Lead) System, JPE 12, 73-77 (1991). [doi:10.1007/bf02663678](https://doi.org/10.1007/bf02663678)
4. Yubi Zhang, Changrong Li, Zhenmin Du, Tai Geng, The thermodynamic assessment of the Co–Sb system, Calphad 32, 56-63 (2008). [doi:10.1016/j.calphad.2007.11.001](https://doi.org/10.1016/j.calphad.2007.11.001)
5. William Golumbfskie, Zi-Kui Liu, CALPHAD/first-principles re-modeling of the Co–Y binary system, Journal of Alloys and Compounds 407, 193-200 (2006). [doi:10.1016/j.jallcom.2005.06.037](https://doi.org/10.1016/j.jallcom.2005.06.037)
6. Marlena Ostrowska, Gabriele Cacciamani, Critical evaluation and thermodynamic modeling of the Al-Co-Fe system, Journal of Alloys and Compounds 794, 553-568 (2019). [doi:10.1016/j.jallcom.2019.04.170](https://doi.org/10.1016/j.jallcom.2019.04.170)
7. Ming Chen, Bengt Hallstedt, Ludwig J. Gauckler, Thermodynamic assessment of the Co-O system, JPE 24, 212-227 (2003). [doi:10.1361/105497103770330514](https://doi.org/10.1361/105497103770330514)
8. A. Davydov, U. R. Kattner, Thermodynamic assessment of the Co-Mo system, JPE 20, 5-16 (1999). [doi:10.1361/105497199770335893](https://doi.org/10.1361/105497199770335893)
9. Jaroslav Kubišta, Jan Vřešt’ál, Thermodynamics of the liquid Co-Cu system and calculation of phase diagram, JPE 21, 125-129 (2000). [doi:10.1361/105497100770340165](https://doi.org/10.1361/105497100770340165)
10. DongEung Kim, James E. Saal, Liangcai Zhou, ShunLi Shang, Yong Du, Zi-Kui Liu, Thermodynamic modeling of fcc order/disorder transformations in the Co–Pt system, Calphad 35, 323-330 (2011). [doi:10.1016/j.calphad.2011.04.005](https://doi.org/10.1016/j.calphad.2011.04.005)
11. G. Cacciamani, R. Ferro, I. Ansara, N. Dupin, Thermodynamic modelling of the Co–Ti system, Intermetallics 8, 213-222 (2000). [doi:10.1016/s0966-9795(99)00098-9](https://doi.org/10.1016/s0966-9795%2899%2900098-9)
12. Chenyang Zhou, Cuiping Guo, Jingbo Li, Changrong Li, Zhenmin Du, Key Experiments and Thermodynamic Description of the Co-Nb-Ni System, Metall Mater Trans A 51, 5892-5911 (2020). [doi:10.1007/s11661-020-05963-2](https://doi.org/10.1007/s11661-020-05963-2)

## 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 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_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/).