# Co–O system

> Co–O system: 120 accepted literature values (model expression 73, invariant reaction 19, formation 10, phase transition 10) and 1 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

120 accepted literature values from 1 paper(s) (experimental 91, model 29); 1 calculated phase diagram(s). 7 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/CO-O.json) · [CSV](https://data.orchid-project.org/systems/CO-O.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#CO-O) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#CO-O/CoO-03Che-LB.json) · [phases (9)](https://data.orchid-project.org/phases/pages/CO-O.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/CO-O.html) · [Markdown](https://data.orchid-project.org/systems/CO-O.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 91 |
| model | 29 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 19 |
| phase transition | 10 |
| formation | 10 |
| heat capacity / entropy / enthalpy | 8 |
| model expression | 73 |

## 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 |
|---|---|---|---|
| CoO-03Che-LB.tdb | M. Chen, B. Hallstedt, L.J. Gauckler, J. Phase Equilib., 24, 212-27(2003). [doi:10.1361/105497103770330514](https://doi.org/10.1361/105497103770330514) | `6da44079fa3d4ae1ab1d1023b514c1f899ec754ee50223c5c3dc2084aff2fa64` | [viewer](https://orchid-project.org/phase-diagrams/#CO-O/CoO-03Che-LB.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/CoO-03Che-LB.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/CoO-03Che-LB.json) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/CO/CO-O.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/CO/CO-O.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Co–O system (19)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 2208 | congruent melting: L2 -> CoO | L2: Co 0.5, O 0.5; CoO: Co 0.5, O 0.5 | experimental | [1] Chen 2003; _cites H 1931_ | Table 8, p. 12, row 7; `ORC-Y5ZWKNPHJZ` |  |
| 2103 | congruent melting: L2 -> CoO | L2: Co 0.5, O 0.5; CoO: Co 0.5, O 0.5 | experimental | [1] Chen 2003; _cites Chase 1985_ | Table 8, p. 12, row 9; `ORC-LWIJFXLMZH` |  |
| 2097 | congruent melting: L2 -> CoO | L2: Co 0.5, O 0.5; CoO: Co 0.5, O 0.5 | model | [1] Chen 2003 | Table 8, p. 12, row 10; `ORC-I3NQBQVBOB` |  |
| 2083 | congruent melting: L2 -> CoO | L2: Co 0.5, O 0.5; CoO: Co 0.5, O 0.5 | experimental | [1] Chen 2003; _cites H 1932_ | Table 8, p. 12, row 8; `ORC-5SNADZPQIZ` |  |
| 1766 | eutectic: L1 -> Co(fcc) + CoO | L1: O 0.0044 | model | [1] Chen 2003 | Table 8, p. 12, row 6; `ORC-ZATOZR3UID` |  |
| 1763 | eutectic |  | experimental | [1] Chen 2003; _cites Jacob 1985_ | p. 1; `ORC-II3DA2EKJ2` | “The most recently determined Co-CoO eutectic point, by Jacob and Hajra \[1985Jac\], is at T ⳱ 1763 K and xO ⳱ 0.0048.” |
| 1763 | eutectic: L1 -> Co(fcc) + CoO | L1: O 0.0048 | experimental | [1] Chen 2003; _cites Jacob 1985_ | Table 8, p. 12, row 5; `ORC-VM7FIXNCRM` |  |
| 1730 | eutectic: L1 -> Co(fcc) + CoO |  | experimental | [1] Chen 2003; _cites Taskinen 1983_ | Table 8, p. 12, row 4; `ORC-BKT5NQFRUC` |  |
| 1730 | eutectic |  | experimental | [1] Chen 2003; _cites Taskinen 1983_ | p. 1; `ORC-WTOLAVF5HS.bcbe4c` | “Based on electromotive force (EMF) measurements of the equilibria of Co(s)CoO(s) and Co(l)-CoO(s), Kemori et al. \[1977Kem\] determined the eutectic temperature of Co-CoO as 1727 K while Taskinen \[1983Tas\] gave a value of 1730 K.” |
| 1727 | eutectic |  | experimental | [1] Chen 2003; _cites Kemori 1977_ [doi](https://doi.org/10.2320/jinstmet1952.41.8_803) | p. 1; `ORC-WTOLAVF5HS.fcf9cf` | “Based on electromotive force (EMF) measurements of the equilibria of Co(s)CoO(s) and Co(l)-CoO(s), Kemori et al. \[1977Kem\] determined the eutectic temperature of Co-CoO as 1727 K while Taskinen \[1983Tas\] gave a value of 1730 K.” |
| 1727 | eutectic: L1 -> Co(fcc) + CoO |  | experimental | [1] Chen 2003; _cites Kemori 1977_ [doi](https://doi.org/10.2320/jinstmet1952.41.8_803) | Table 8, p. 12, row 3; `ORC-ZWMISWXGSO` |  |
| 1724 | eutectic: L1 -> Co(fcc) + CoO | L1: O 0.0084 | experimental | [1] Chen 2003; _cites Hansen 1958_ | Table 8, p. 12, row 2; `ORC-XSFWUHFAVU` |  |
| 1719 | eutectic: L1 -> Co(fcc) + CoO | L1: O 0.0095 | experimental | [1] Chen 2003; _cites ref. 1951Aa_ | Table 8, p. 12, row 1; `ORC-SZQJGVT2AV` |  |
| 1719 | eutectic |  | experimental | [1] Chen 2003; _cites Asanti 1951_ [doi](https://doi.org/10.1002/zaac.19512650110) | p. 1; `ORC-VNKYXJVDQL` | “Asanti and Kohlmeyer \[1951Asa\] measured the eutectic of Co-CoO and determined the eutectic point to be at approximately T ⳱ 1719 K and xO ⳱ 0.0095.” |
| 1233 | 3CoO + 0.5O2 -> Co3O4 (in 1 bar O2) | Co3O4: Co 0.428571, O 0.571429 | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 8, p. 12, row 14; `ORC-3VB2QKHJVX` |  |
| 1224 | 3CoO + 0.5O2 -> Co3O4 (in 1 bar O2) | Co3O4: Co 0.428571, O 0.571429 | model | [1] Chen 2003 | Table 8, p. 12, row 15; `ORC-4OK7ZX4SGV` |  |
| 1173 | 3CoO + 0.5O2 -> Co3O4 (in air) | Co3O4: Co 0.428571, O 0.571429 | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 8, p. 12, row 12; `ORC-FOZL77SP7L` |  |
| 1170 | 3CoO + 0.5O2 -> Co3O4 (in air) | Co3O4: Co 0.428571, O 0.571429 | experimental | [1] Chen 2003; _cites Sreedharan 1977_ | Table 8, p. 12, row 11; `ORC-DTQJC7E2S7` |  |
| 1170 | 3CoO + 0.5O2 -> Co3O4 (in air) | Co3O4: Co 0.428571, O 0.571429 | model | [1] Chen 2003 | Table 8, p. 12, row 13; `ORC-M5G4I2KTQB` |  |

## 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–O system (10)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Co3O4 | [Co3O4](https://data.orchid-project.org/compounds/Co3O4.html) | -130.77 kJ/mol-atom | 298.15 | model | -125.536 (mp-aaacujjd) | -129.587 (oqmd-4562) | [1] Chen 2003 | Table 5, p. 10, row 7; `ORC-6CA7FA2MAK.daaed4` |  |
| Co3O4 | [Co3O4](https://data.orchid-project.org/compounds/Co3O4.html) | -130 kJ/mol-atom | 298.15 | model | -125.536 (mp-aaacujjd) | -129.587 (oqmd-4562) | [1] Chen 2003; _cites Chase 1985_ | Table 5, p. 10, row 6; `ORC-CWHCU6KGXD.e87886` |  |
| Co3O4 | [Co3O4](https://data.orchid-project.org/compounds/Co3O4.html) | -127.286 kJ/mol-atom | 298.15 | model | -125.536 (mp-aaacujjd) | -129.587 (oqmd-4562) | [1] Chen 2003; _cites Wagman 1969_ | Table 5, p. 10, row 4; `ORC-MT6IPPMHOI.ee40bd` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -120.29 kJ/mol-atom | 298.15 | experimental | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Mixter 1910_ [doi](https://doi.org/10.2475/ajs.s4-30.177.193) | Table 5, p. 10, row 1; `ORC-PDP2R4RQRL` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -120.29 kJ/mol-atom | 298.15 | experimental | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Roth 1931_ [doi](https://doi.org/10.1002/zaac.19311950125) | Table 5, p. 10, row 2; `ORC-YY6S4JS6II` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -119.45 kJ/mol-atom | 298.15 | experimental | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Boyle 1954_ [doi](https://doi.org/10.1021/ja01643a072) | Table 5, p. 10, row 3; `ORC-V546TAYISH` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -118.97 kJ/mol-atom | 298.15 | model | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Wagman 1969_ | Table 5, p. 10, row 4; `ORC-MT6IPPMHOI.77ac43` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -118.85 kJ/mol-atom | 298.15 | model | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Chase 1985_ | Table 5, p. 10, row 6; `ORC-CWHCU6KGXD.7fb507` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -118.75 kJ/mol-atom | 298.15 | model | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003; _cites Cyr 1981_ [doi](https://doi.org/10.1021/je00025a030) | Table 5, p. 10, row 5; `ORC-WHMXOZSXAH` |  |
| CoO | [CoO](https://data.orchid-project.org/compounds/CoO.html) | -118.43 kJ/mol-atom | 298.15 | model | -123.923 (mp-aaaabhdw) | -123.858 (oqmd-2169004) | [1] Chen 2003 | Table 5, p. 10, row 7; `ORC-6CA7FA2MAK.f62029` |  |

## Other properties

### Phase transition (10)

Table: Phase transition, Co–O system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 33 K | 33 | magnetic | experimental | [1] Chen 2003; _cites Chibirova 1984_ | p. 3; `ORC-A7HOYYBVUI.a72fc7` | “Co3O4 has been found to undergo a transition from paramagnetic state to antiferromagnetic state at 40 K \[1964Rot\] or 33 K \[1984Chi\].” |
| Phase transition | 40 K | 40 | magnetic | experimental | [1] Chen 2003; _cites Roth 1964_ [doi](https://doi.org/10.1016/0022-3697%2864%2990156-8) | p. 3; `ORC-A7HOYYBVUI.f71333` | “Co3O4 has been found to undergo a transition from paramagnetic state to antiferromagnetic state at 40 K \[1964Rot\] or 33 K \[1984Chi\].” |
| Phase transition | 290 K | 290 | magnetic | experimental | [1] Chen 2003; _cites Jauch 2003_ | p. 3; `ORC-B7YDG7X47M` | “At low temperature, CoO is an antiferromagnetic compound with a Néel temperature of TN ≈ 290 K \[2001Jau\].” |
| Phase transition | 695 K | 695 | hcp + fcc | model | [1] Chen 2003; _cites Nishizawa 1983_ [doi](https://doi.org/10.1007/bf02868089) | p. 6; `ORC-6JHGTULJHG` | “In the recent review papers on the thermodynamic properties of cobalt metal \[1983Nis, 1987Gui, 1990Mas\], the stable temperature range for the hcp phase is below 695 K; the range for the fcc phase is from 695 K up to its melting point.” |
| Phase transition | 1170 K | 1170 | other | experimental | [1] Chen 2003 | p. 1; `ORC-OOXYZTUJI5` | “Co3O4 decomposes at about 1170 K (in air), and CoO is stable up to its melting point, given as 2083 K \[1932War\] and 2103 K \[1985Cha\].” |
| Phase transition | 1768 K | 1768 | α-Co + liquid | experimental | [1] Chen 2003 | p. 1; `ORC-6S4BZ4MCFW` | “The melting point of ␣-Co is 1768 K.” |
| Phase transition | 2083 K | 2083 | congruent melting | experimental | [1] Chen 2003; _cites H 1932_ | p. 1; `ORC-FWUEKXB4UK.d43092` | “The earliest measurement on the congruent melting point of CoO was done by Wartenberg and Gurr \[1931War\], giving a value of 2208 K, but it was soon corrected to 2083 K \[1932War\].” |
| Phase transition | 2097 K | 2097 | congruent transformation | model | [1] Chen 2003 | p. 12; `ORC-VQAZRGX4XH` | “The calculated congruent melting point of CoO is 2097 K, in reasonable agreement with the JANAF tables \[1985Cha\].” |
| Phase transition | 2103 K | 2103 | CoO + liquid | experimental | [1] Chen 2003; _cites Chase 1985_ | p. 1; `ORC-KGYPE3JGFC` | “The JANAF tables \[1985Cha\] adopt 2103 ± 10 K as Tfus. for CoO based on the work of Coutures and Foëx \[1972Cou\].” |
| Phase transition | 2208 K | 2208 | congruent melting | experimental | [1] Chen 2003; _cites H 1931_ | p. 1; `ORC-FWUEKXB4UK.0e0e7f` | “The earliest measurement on the congruent melting point of CoO was done by Wartenberg and Gurr \[1931War\], giving a value of 2208 K, but it was soon corrected to 2083 K \[1932War\].” |

### Heat capacity / entropy / enthalpy (8)

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

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: S (Co3O4)_ | 15.6286 J/mol-atom/K | 298.15 | Co3O4; _alloy: O 0.571429_ | model | [1] Chen 2003 | Table 6, p. 10, row 5; `ORC-JEHXCEXTYA.bd7d5a` |  |
| Entropy; _printed: S (Co3O4)_ | 15.6143 J/mol-atom/K | 298.15 | Co3O4; _alloy: O 0.571429_ | experimental | [1] Chen 2003; _cites Khriplovich 1982_ [doi](https://doi.org/10.1016/0021-9614%2882%2990012-x) | Table 6, p. 10, row 2; `ORC-MMFZ5D4GHC` |  |
| Entropy; _printed: S (Co3O4)_ | 14.6429 J/mol-atom/K | 298.15 | Co3O4; _alloy: O 0.571429_ | experimental | [1] Chen 2003; _cites King 1957_ [doi](https://doi.org/10.1021/ja01567a016) | Table 6, p. 10, row 1; `ORC-WQR5MAUTRO.6414c4` |  |
| Entropy; _printed: S (Co3O4)_ | 16.3271 J/mol-atom/K | 298.15 | Co3O4; _alloy: O 0.571429_ | model | [1] Chen 2003; _cites Chase 1985_ | Table 6, p. 10, row 4; `ORC-XNDN5U3S75.f4f52b` |  |
| Entropy; _printed: S (CoO)_ | 27.155 J/mol-atom/K | 298.15 | CoO; _alloy: O 0.5_ | model | [1] Chen 2003 | Table 6, p. 10, row 5; `ORC-JEHXCEXTYA.710b91` |  |
| Entropy; _printed: S (CoO)_ | 26.415 J/mol-atom/K | 298.15 | CoO; _alloy: O 0.5_ | experimental | [1] Chen 2003; _cites Nabutovskaya 1985_ | Table 6, p. 10, row 3; `ORC-TTCJKT7JBF` |  |
| Entropy; _printed: S (CoO)_ | 26.485 J/mol-atom/K | 298.15 | CoO; _alloy: O 0.5_ | experimental | [1] Chen 2003; _cites King 1957_ [doi](https://doi.org/10.1021/ja01567a016) | Table 6, p. 10, row 1; `ORC-WQR5MAUTRO.e410ad` |  |
| Entropy; _printed: S (CoO)_ | 26.4965 J/mol-atom/K | 298.15 | CoO; _alloy: O 0.5_ | model | [1] Chen 2003; _cites Chase 1985_ | Table 6, p. 10, row 4; `ORC-XNDN5U3S75.976eed` |  |

### Model expression (73)

Table: Model expression, Co–O system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 177.58 J/mol/K |  | UNKNOWN | model | [1] Chen 2003 | Table 3, p. 9, row 27; `ORC-2WCUYBHQAN.748f84` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -213459 J/mol |  | UNKNOWN | model | [1] Chen 2003 | Table 3, p. 9, row 27; `ORC-2WCUYBHQAN.d8f974` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -215413 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Sreedharan 1977_ | Table 3, p. 9, row 14; `ORC-6L5FIOH67M.0c3755` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 180.15 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Sreedharan 1977_ | Table 3, p. 9, row 14; `ORC-6L5FIOH67M.63f278` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 138.616 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1965_ | Table 3, p. 9, row 8; `ORC-AHSDMXE4NZ.891a37` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -171251 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1965_ | Table 3, p. 9, row 8; `ORC-AHSDMXE4NZ.f30841` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -207759 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 3, p. 9, row 24; `ORC-BLXVJGSZMP.4158a7` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 172.606 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 3, p. 9, row 24; `ORC-BLXVJGSZMP.b947d6` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 144.197 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Grimsey 1986_ [doi](https://doi.org/10.1016/0021-9614%2886%2990095-9) | Table 3, p. 9, row 23; `ORC-BQRLR65FOI.363fda` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -188824 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Grimsey 1986_ [doi](https://doi.org/10.1016/0021-9614%2886%2990095-9) | Table 3, p. 9, row 23; `ORC-BQRLR65FOI.88012c` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 130.44 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1985_ | Table 3, p. 9, row 22; `ORC-D2AIBLYYTE.6efec9` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -161071 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1985_ | Table 3, p. 9, row 22; `ORC-D2AIBLYYTE.c0c738` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -201995 J/mol |  | UNKNOWN | model | [1] Chen 2003; _cites Chase 1985_ | Table 3, p. 9, row 26; `ORC-D6QHFRA4JI.aa31fd` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 165.062 J/mol/K |  | UNKNOWN | model | [1] Chen 2003; _cites Chase 1985_ | Table 3, p. 9, row 26; `ORC-D6QHFRA4JI.eac437` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -212713 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1985_ | Table 3, p. 9, row 21; `ORC-GRNZPQCJVF.4555d8` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 175.972 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites ref. 1985_ | Table 3, p. 9, row 21; `ORC-GRNZPQCJVF.5d324b` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 162.545 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bugden 1970_ | Table 3, p. 9, row 10; `ORC-KTGJYDVQRS.9e8bd3` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -197142 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bugden 1970_ | Table 3, p. 9, row 10; `ORC-KTGJYDVQRS.cfc279` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 165.433 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bugden 1970_ | Table 3, p. 9, row 9; `ORC-L5QT5VAIWT.30a79c` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -200022 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bugden 1970_ | Table 3, p. 9, row 9; `ORC-L5QT5VAIWT.abc12c` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -169432 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Melnik 1974_ | Table 3, p. 9, row 12; `ORC-LBXR47ODHV.351b86` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 137.515 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Melnik 1974_ | Table 3, p. 9, row 12; `ORC-LBXR47ODHV.ae28c5` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -191643 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Enoki 1977_ [doi](https://doi.org/10.2320/jinstmet1952.41.5_505) | Table 3, p. 9, row 13; `ORC-MBHNS4GUOA.3f0909` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 153.282 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Enoki 1977_ [doi](https://doi.org/10.2320/jinstmet1952.41.5_505) | Table 3, p. 9, row 13; `ORC-MBHNS4GUOA.d84967` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 122.668 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Ingraham 1964_ [doi](https://doi.org/10.1179/cmq.1964.3.3.221) | Table 3, p. 9, row 6; `ORC-MJV5D3DTSX.580918` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -151244 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Ingraham 1964_ [doi](https://doi.org/10.1179/cmq.1964.3.3.221) | Table 3, p. 9, row 6; `ORC-MJV5D3DTSX.5b3d25` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 129.381 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 3, p. 9, row 25; `ORC-N4M2XGTUEO.1afa28` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -159324 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Kale 1988_ [doi](https://doi.org/10.2320/matertrans1960.29.125) | Table 3, p. 9, row 25; `ORC-N4M2XGTUEO.fe1039` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -108698 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Biltz 1907_ | Table 3, p. 9, row 1; `ORC-NBNVU56QZ4.6dd6fd` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 85.958 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Biltz 1907_ | Table 3, p. 9, row 1; `ORC-NBNVU56QZ4.8210a9` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 128.332 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Watanabe 1933_ | Table 3, p. 9, row 3; `ORC-NLW6ZVXXBO.0b8614` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -161074 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Watanabe 1933_ | Table 3, p. 9, row 3; `ORC-NLW6ZVXXBO.32ce47` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 140.219 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Narducci 1985_ [doi](https://doi.org/10.1016/0254-0584%2885%2990107-5) | Table 3, p. 9, row 20; `ORC-OOQ6PFPLEM.9c2085` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -172172 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Narducci 1985_ [doi](https://doi.org/10.1016/0254-0584%2885%2990107-5) | Table 3, p. 9, row 20; `ORC-OOQ6PFPLEM.a7b8cf` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -165686 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Alcock 1965_ | Table 3, p. 9, row 7; `ORC-PEY6APS45Z.0253d4` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 135.771 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Alcock 1965_ | Table 3, p. 9, row 7; `ORC-PEY6APS45Z.6e18c8` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 150.334 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Chizhikov 1972_ | Table 3, p. 9, row 11; `ORC-PG3OZZ3BIY.4b88c5` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -179962 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Chizhikov 1972_ | Table 3, p. 9, row 11; `ORC-PG3OZZ3BIY.f140bd` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 189.972 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Koumoto 1981_ [doi](https://doi.org/10.1143/jjap.20.445) | Table 3, p. 9, row 18; `ORC-POYWY6TTNO.3fb2ee` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -223995 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Koumoto 1981_ [doi](https://doi.org/10.1143/jjap.20.445) | Table 3, p. 9, row 18; `ORC-POYWY6TTNO.b616b2` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -147573 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Balakirev 1961_ | Table 3, p. 9, row 5; `ORC-PZCX3V666A.166ebd` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 118.051 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Balakirev 1961_ | Table 3, p. 9, row 5; `ORC-PZCX3V666A.47f1ee` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 147.875 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Flamand 1984_ | Table 3, p. 9, row 19; `ORC-QQ5PVZUIYL.97510b` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -181187 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Flamand 1984_ | Table 3, p. 9, row 19; `ORC-QQ5PVZUIYL.e39109` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -146890 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Foote 1908_ [doi](https://doi.org/10.1021/ja01951a002) | Table 3, p. 9, row 2; `ORC-R4ZD4VRTIJ.9d9c6d` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 118.266 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Foote 1908_ [doi](https://doi.org/10.1021/ja01951a002) | Table 3, p. 9, row 2; `ORC-R4ZD4VRTIJ.b4235f` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -122011 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Chufarov 1950_ | Table 3, p. 9, row 4; `ORC-T4RLOJITNH.badf81` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 94.855 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Chufarov 1950_ | Table 3, p. 9, row 4; `ORC-T4RLOJITNH.e5f327` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T ln T)_ | -258.981 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bjorkman 1979_ | Table 3, p. 9, row 16; `ORC-V3LAHR6NTN.3fe4ab` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 2219.6 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bjorkman 1979_ | Table 3, p. 9, row 16; `ORC-V3LAHR6NTN.502e06` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -463419 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Bjorkman 1979_ | Table 3, p. 9, row 16; `ORC-V3LAHR6NTN.d093f5` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 140.226 J/mol/K |  | UNKNOWN | model | [1] Chen 2003 | Table 3, p. 9, row 28; `ORC-WO7ALJWO3Z.20fb7b` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -171649 J/mol |  | UNKNOWN | model | [1] Chen 2003 | Table 3, p. 9, row 28; `ORC-WO7ALJWO3Z.2f5396` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -167564 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Sreedharan 1977_ | Table 3, p. 9, row 15; `ORC-WUENY7IROL.9767b7` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 77.593 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Sreedharan 1977_ | Table 3, p. 9, row 15; `ORC-WUENY7IROL.ec7efe` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A)_ | -165220 J/mol |  | UNKNOWN | experimental | [1] Chen 2003; _cites Oppermann 1980_ [doi](https://doi.org/10.1002/zaac.19804610126) | Table 3, p. 9, row 17; `ORC-X65QXBCISV.1c3eaa` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient of T)_ | 135.851 J/mol/K |  | UNKNOWN | experimental | [1] Chen 2003; _cites Oppermann 1980_ [doi](https://doi.org/10.1002/zaac.19804610126) | Table 3, p. 9, row 17; `ORC-X65QXBCISV.c6dd17` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -61504.8 J/mol |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Tankins 1964_ | Table 7, p. 11, row 1; `ORC-GM3CIC2AYR.728679` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -20.489 J/mol/K |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Tankins 1964_ | Table 7, p. 11, row 1; `ORC-GM3CIC2AYR.cc905a` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -0.326 J/mol/K |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Fischer 1966_ [doi](https://doi.org/10.1002/srin.196602732) | Table 7, p. 11, row 2; `ORC-INDWBMMV5A.8128f6` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -98240 J/mol |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Fischer 1966_ [doi](https://doi.org/10.1002/srin.196602732) | Table 7, p. 11, row 2; `ORC-INDWBMMV5A.edc42e` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -61630 J/mol |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003; _cites Sigworth 1976_ [doi](https://doi.org/10.1179/cmq.1976.15.2.123) | Table 7, p. 11, row 6; `ORC-JF4BLIJOXU.50a832` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -20.493 J/mol/K |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003; _cites Sigworth 1976_ [doi](https://doi.org/10.1179/cmq.1976.15.2.123) | Table 7, p. 11, row 6; `ORC-JF4BLIJOXU.5e6e3d` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -90984 J/mol |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003 | Table 7, p. 11, row 9; `ORC-LDPCJMATTP.8e9445` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -4.292 J/mol/K |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003 | Table 7, p. 11, row 9; `ORC-LDPCJMATTP.f3749f` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -16.681 J/mol/K |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003; _cites Chiang 1976_ [doi](https://doi.org/10.1007/bf02652717) | Table 7, p. 11, row 5; `ORC-QDGFUWND5E.ab2387` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -67613 J/mol |  | liquid Co; _alloy: O 0_ | model | [1] Chen 2003; _cites Chiang 1976_ [doi](https://doi.org/10.1007/bf02652717) | Table 7, p. 11, row 5; `ORC-QDGFUWND5E.c45611` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -72467 J/mol |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Belov 1967_ | Table 7, p. 11, row 3; `ORC-TLHUQCK7UK.3ca308` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -13.086 J/mol/K |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Belov 1967_ | Table 7, p. 11, row 3; `ORC-TLHUQCK7UK.f7bef1` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -7.555 J/mol/K |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Jacob 1985_ | Table 7, p. 11, row 8; `ORC-WTMUSMAFJQ.d59882` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -84935 J/mol |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Jacob 1985_ | Table 7, p. 11, row 8; `ORC-WTMUSMAFJQ.dee6ec` |  |
| gibbs energy expression term; _printed: ΔG° (coefficient B of A + B·T)_ | -4.181 J/mol/K |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Janke 1978_ | Table 7, p. 11, row 7; `ORC-YC6MZA5BT3.d7482e` |  |
| gibbs energy expression term; _printed: ΔG° (constant term A of A + B·T)_ | -91335 J/mol |  | liquid Co; _alloy: O 0_ | experimental | [1] Chen 2003; _cites Janke 1978_ | Table 7, p. 11, row 7; `ORC-YC6MZA5BT3.d9942e` |  |

## Sources

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

1. 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)

## 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/).