# Co–Hf system

> Co–Hf system: 60 accepted literature values (invariant reaction 31, heat capacity / entropy / enthalpy 20, formation 8, other property 1) and 3 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

60 accepted literature values from 2 paper(s) (experimental 42, model 18); 3 calculated phase diagram(s). 10 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-HF.json) · [CSV](https://data.orchid-project.org/systems/CO-HF.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#CO-HF) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#CO-HF/CoHf-06Bra.json) · [phases (11)](https://data.orchid-project.org/phases/pages/CO-HF.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/CO-HF.html) · [Markdown](https://data.orchid-project.org/systems/CO-HF.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 42 |
| model | 18 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 31 |
| formation | 8 |
| heat capacity / entropy / enthalpy | 20 |
| 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 |
|---|---|---|---|
| CoHf-06Bra.tdb | J. Bratberg, B. Jansson, J. Phase Equilib. Diffus., 27, 213-19(2006). [doi:10.1361/154770306X109746](https://doi.org/10.1361/154770306X109746) | `046d63a555f58b794af1dd2ad9bebcefffd41460a93bd2c77022a937010696ec` | [viewer](https://orchid-project.org/phase-diagrams/#CO-HF/CoHf-06Bra.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/CoHf-06Bra.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/CoHf-06Bra.json) |
| CoHf-15Lu.tdb | X. Lu, S. Liu, K. Cheng, Y. Tang, P. Ou, P. Nash, B. Sundman, Y. Du, F. Zheng, Thermochim. Acta, 608, 49-58(2015). [doi:10.1016/j.tca.2015.04.004](https://doi.org/10.1016/j.tca.2015.04.004) | `dffa8495cab9319c36b1181ed0b46493b6f6a38ca666c3f259650656dafa9d5a` | [viewer](https://orchid-project.org/phase-diagrams/#CO-HF/CoHf-15Lu.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/CoHf-15Lu.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/CoHf-15Lu.json) |
| CoHf-18Hua.tdb | X.M. Huang, W.J. Zeng, J.L. Liu, G.M. Cai, S.H. Liu, H.S. Liu, Z.P. Jin, Calphad, 62, 128-40(2018). [doi:10.1016/j.calphad.2018.06.002](https://doi.org/10.1016/j.calphad.2018.06.002) | `065a8d8f49f9e2c1ff641f771f5794cfd28b892b392fd1b87cde6cd2828a504e` | [viewer](https://orchid-project.org/phase-diagrams/#CO-HF/CoHf-18Hua.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/CoHf-18Hua.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/CoHf-18Hua.json) |

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

| TDB file | T (K) | Phases at the invariant |
|---|---:|---|
| CoHf-06Bra.tdb | 1996.02 | CO2HF_C15 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.43162) + COHF_B2 (x(Hf) 0.5) |
| CoHf-06Bra.tdb | 1996.02 | CO2HF_C15 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.4317) + COHF_B2 (x(Hf) 0.5) |
| CoHf-06Bra.tdb | 1996.02 | CO2HF_C15 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.43131) + COHF_B2 (x(Hf) 0.5) |
| CoHf-06Bra.tdb | 1699.29 | COHF_B2 (x(Hf) 0.5) + COHF2 (x(Hf) 0.66667) + LIQUID (x(Hf) 0.71925) |
| CoHf-06Bra.tdb | 1699.29 | COHF_B2 (x(Hf) 0.5) + COHF2 (x(Hf) 0.66667) + LIQUID (x(Hf) 0.719) |
| CoHf-06Bra.tdb | 1674.1 | COHF2 (x(Hf) 0.66667) + LIQUID (x(Hf) 0.74745) + BCC_A2 (x(Hf) 0.84811) |
| CoHf-06Bra.tdb | 1674.1 | COHF2 (x(Hf) 0.66667) + LIQUID (x(Hf) 0.74747) + BCC_A2 (x(Hf) 0.84814) |
| CoHf-06Bra.tdb | 1566.66 | FCC_A1 (x(Hf) 0.01466) + LIQUID (x(Hf) 0.08452) + CO2HF_C15 (x(Hf) 0.33333) |
| CoHf-06Bra.tdb | 1485.33 | COHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.90157) + HCP_A3 (x(Hf) 0.99019) |
| CoHf-06Bra.tdb | 1485.33 | COHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.90159) + HCP_A3 (x(Hf) 0.9902) |
| CoHf-06Bra.tdb | 694.96 | FCC_A1 (x(Hf) 0) + HCP_A3 (x(Hf) 0) + CO2HF_C15 (x(Hf) 0.33333) |
| CoHf-15Lu.tdb | 1838.87 | C15_LAVES (x(Hf) 0.34687) + LIQUID (x(Hf) 0.41529) + B2_BCC (x(Hf) 0.48209) |
| CoHf-15Lu.tdb | 1599.97 | LIQUID (x(Hf) 0.14555) + CO23HF6_D8A (x(Hf) 0.2069) + C15_LAVES (x(Hf) 0.25028) |
| CoHf-15Lu.tdb | 1579.78 | B2_BCC (x(Hf) 0.51408) + COHF2 (x(Hf) 0.65937) + LIQUID (x(Hf) 0.67952) |
| CoHf-15Lu.tdb | 1550.86 | COHF2 (x(Hf) 0.67721) + LIQUID (x(Hf) 0.71913) + B2_BCC (x(Hf) 0.8747) |
| CoHf-15Lu.tdb | 1545.48 | LIQUID (x(Hf) 0.11606) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-15Lu.tdb | 1545.48 | LIQUID (x(Hf) 0.11583) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-15Lu.tdb | 1516.92 | FCC_A1 (x(Hf) 0.00552) + LIQUID (x(Hf) 0.09453) + CO11HF2 (x(Hf) 0.15385) |
| CoHf-15Lu.tdb | 1516.92 | FCC_A1 (x(Hf) 0.00552) + LIQUID (x(Hf) 0.09449) + CO11HF2 (x(Hf) 0.15385) |
| CoHf-15Lu.tdb | 1476.55 | COHF2 (x(Hf) 0.68042) + B2_BCC (x(Hf) 0.88613) + HCP_A3 (x(Hf) 0.97783) |
| CoHf-15Lu.tdb | 928.48 | FCC_A1 (x(Hf) 3.000e-5) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-15Lu.tdb | 928.48 | FCC_A1 (x(Hf) 3.000e-5) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-15Lu.tdb | 694.98 | HCP_A3 (x(Hf) 0) + FCC_A1 (x(Hf) 0) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-18Hua.tdb | 1838.87 | C15_LAVES (x(Hf) 0.34687) + LIQUID (x(Hf) 0.41529) + B2_BCC (x(Hf) 0.48209) |
| CoHf-18Hua.tdb | 1599.97 | LIQUID (x(Hf) 0.14555) + CO23HF6_D8A (x(Hf) 0.2069) + C15_LAVES (x(Hf) 0.25028) |
| CoHf-18Hua.tdb | 1579.78 | B2_BCC (x(Hf) 0.51408) + COHF2 (x(Hf) 0.65937) + LIQUID (x(Hf) 0.67952) |
| CoHf-18Hua.tdb | 1550.86 | COHF2 (x(Hf) 0.67721) + LIQUID (x(Hf) 0.71913) + B2_BCC (x(Hf) 0.8747) |
| CoHf-18Hua.tdb | 1545.8 | LIQUID (x(Hf) 0.11614) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-18Hua.tdb | 1545.79 | LIQUID (x(Hf) 0.11597) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-18Hua.tdb | 1516.31 | FCC_A1 (x(Hf) 0.00821) + LIQUID (x(Hf) 0.09564) + CO11HF2 (x(Hf) 0.15385) |
| CoHf-18Hua.tdb | 1516.31 | FCC_A1 (x(Hf) 0.0082) + LIQUID (x(Hf) 0.09561) + CO11HF2 (x(Hf) 0.15385) |
| CoHf-18Hua.tdb | 1476.55 | COHF2 (x(Hf) 0.68042) + B2_BCC (x(Hf) 0.88613) + HCP_A3 (x(Hf) 0.97783) |
| CoHf-18Hua.tdb | 1308.42 | FCC_A1 (x(Hf) 0.00219) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-18Hua.tdb | 1308.42 | FCC_A1 (x(Hf) 0.00219) + CO11HF2 (x(Hf) 0.15385) + CO23HF6_D8A (x(Hf) 0.2069) |
| CoHf-18Hua.tdb | 694.98 | HCP_A3 (x(Hf) 0) + FCC_A1 (x(Hf) 0) + CO23HF6_D8A (x(Hf) 0.2069) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/CO/CO-HF.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/CO/CO-HF.json) · [CALPHAD hull CoHf-06Bra](https://data.orchid-project.org/hulls/calphad-sgte/CO/CO-HF--CoHf-06Bra.json) · [CALPHAD hull CoHf-15Lu](https://data.orchid-project.org/hulls/calphad-sgte/CO/CO-HF--CoHf-15Lu.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Co–Hf system (31)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 1943.15 | congruent melting: Liquid -> Co2Hf | Liquid: Hf 0.3333; Co2Hf: Hf 0.3333 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 3; `ORC-ZEDGSLJILU` |  |
| 1913.15 | congruent melting: Liquid -> CoHf | Liquid: Hf 0.5; CoHf: Hf 0.5 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 1; `ORC-IU6PFGEIVW` |  |
| 1898.15 | congruent melting: Liquid -> CoHf | Liquid: Hf 0.4956; CoHf: Hf 0.4956 | model | [1] Lu 2015 | Table 3, p. 6, row 2; `ORC-6T6QTTWVAY` |  |
| 1896.15 | congruent melting: Liquid -> Co2Hf | Liquid: Hf 0.3345; Co2Hf: Hf 0.3345 | model | [1] Lu 2015 | Table 3, p. 6, row 5; `ORC-35DLF5MYUO` |  |
| 1893.15 | congruent melting: Liquid -> Co2Hf | Liquid: Hf 0.3333; Co2Hf: Hf 0.3333 | experimental | [1] Lu 2015; _cites Buschow 1978_ [doi](https://doi.org/10.1016/0022-5088%2878%2990111-x) | Table 3, p. 6, row 4; `ORC-MGBTQCAY2J` |  |
| 1839.15 | eutectic: Liquid -> Co2Hf + CoHf | Liquid: Hf 0.4153; Co2Hf: Hf 0.3468; CoHf: Hf 0.4821 | model | [1] Lu 2015 | Table 3, p. 6, row 7; `ORC-GDJVHZXDML` |  |
| 1823.15 | eutectic: Liquid -> Co2Hf + CoHf | Liquid: Hf 0.435; Co2Hf: Hf 0.375; CoHf: Hf 0.49 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 6; `ORC-AKOGIQ4W7J` |  |
| 1823.15 | eutectic: Liquid -> Co2Hf + CoHf | Liquid: Hf 0.4191; Co2Hf: Hf 0.3428; CoHf: Hf 0.4716 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 8; `ORC-ZPOUPIEDC2` |  |
| 1623.15 | peritectic: Liquid + Co2Hf -> Co23Hf6 | Co2Hf: Co 0.666667, Hf 0.333333; Co23Hf6: Co 0.793103, Hf 0.206897 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 10; `ORC-EW6NAKCDIL` |  |
| 1623.15 | peritectic: Liquid + Co2Hf -> Co23Hf6 | Liquid: Hf 0.135; Co2Hf: Hf 0.27; Co23Hf6: Co 0.793103, Hf 0.206897 | experimental | [1] Lu 2015; _cites Buschow 1978_ [doi](https://doi.org/10.1016/0022-5088%2878%2990111-x) | Table 3, p. 6, row 9; `ORC-XHVSLO6ASH` |  |
| 1600.15 | peritectic: Liquid + Co2Hf -> Co23Hf6 | Liquid: Hf 0.1454; Co2Hf: Hf 0.2501; Co23Hf6: Hf 0.2069 | model | [1] Lu 2015 | Table 3, p. 6, row 12; `ORC-KHTBVXPD3I` |  |
| 1599.15 | peritectic: Liquid + Co2Hf -> Co23Hf6 | Co2Hf: Co 0.666667, Hf 0.333333; Co23Hf6: Co 0.793103, Hf 0.206897 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 11; `ORC-JS2A7AZIT2` |  |
| 1588.15 | peritectic: Liquid + CoHf -> CoHf2 | Liquid: Hf 0.84; CoHf: Hf 0.505; CoHf2: Hf 0.71 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 13; `ORC-RAZRYUCKXW` |  |
| 1585.95 | peritectic: Liquid + CoHf -> CoHf2 | Liquid: Hf 0.69; CoHf: Co 0.5, Hf 0.5; CoHf2: Co 0.333333, Hf 0.666667 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 14; `ORC-T7LRTPMNAB` |  |
| 1580.15 | peritectic: Liquid + CoHf -> CoHf2 | Liquid: Hf 0.6795; CoHf: Hf 0.5141; CoHf2: Hf 0.6594 | model | [1] Lu 2015 | Table 3, p. 6, row 15; `ORC-22SQ6YPT35` |  |
| 1553.15 | eutectic: Liquid -> (αCo) + Co11Hf2 | Liquid: Hf 0.11; (αCo): Hf 0.015; Co11Hf2: Co 0.846154, Hf 0.153846 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 22; `ORC-QDOL3WCUJN` |  |
| 1551.15 | eutectic: Liquid -> CoHf2 + (βHf) | Liquid: Hf 0.7191; CoHf2: Hf 0.6772; (βHf): Hf 0.8747 | model | [1] Lu 2015 | Table 3, p. 6, row 18; `ORC-NAYBBV4KGO` |  |
| 1548.15 | peritectic: Liquid + Co23Hf6 -> Co11Hf2 | Co23Hf6: Co 0.793103, Hf 0.206897; Co11Hf2: Co 0.846154, Hf 0.153846 | experimental | [1] Lu 2015; _cites Buschow 1978_ [doi](https://doi.org/10.1016/0022-5088%2878%2990111-x) | Table 3, p. 6, row 19; `ORC-RPOLJXEGEP` |  |
| 1546.15 | peritectic: Liquid + Co23Hf6 -> Co11Hf2 | Liquid: Hf 0.1161; Co23Hf6: Hf 0.2069; Co11Hf2: Hf 0.1538 | model | [1] Lu 2015 | Table 3, p. 6, row 21; `ORC-4HLAFMPKIH` |  |
| 1546.15 | peritectic: Liquid + Co23Hf6 -> Co11Hf2 | Co23Hf6: Co 0.793103, Hf 0.206897; Co11Hf2: Co 0.846154, Hf 0.153846 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 20; `ORC-LMSWLTNSJE` |  |
| 1544.25 | eutectic: Liquid -> CoHf2 + (βHf) | Liquid: Hf 0.715; CoHf2: Co 0.333333, Hf 0.666667 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 17; `ORC-FK3FXGM5JN` |  |
| 1543.15 | eutectic: Liquid -> CoHf2 + (βHf) | Liquid: Hf 0.86; CoHf2: Hf 0.74; (βHf): Hf 0.95 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 16; `ORC-VHCQZTAUSI` |  |
| 1518.45 | eutectic: Liquid -> (αCo) + Co11Hf2 | Liquid: Hf 0.0965; Co11Hf2: Hf 0.1538 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 24; `ORC-B2EPO62MWO` |  |
| 1517.15 | eutectic: Liquid -> (αCo) + Co11Hf2 | Liquid: Hf 0.0944; (αCo): Hf 0; Co11Hf2: Hf 0.1538 | model | [1] Lu 2015 | Table 3, p. 6, row 25; `ORC-JQE4QPEQJO` |  |
| 1503.15 | eutectic: Liquid -> (αCo) + Co11Hf2 | Co11Hf2: Co 0.846154, Hf 0.153846 | experimental | [1] Lu 2015; _cites Buschow 1978_ [doi](https://doi.org/10.1016/0022-5088%2878%2990111-x) | Table 3, p. 6, row 23; `ORC-IMUPPNBMKL` |  |
| 1477.15 | eutectoid: (βHf) -> CoHf2 + (αHf) | (βHf): Hf 0.8862; CoHf2: Hf 0.6804; (αHf): Hf 0.9778 | model | [1] Lu 2015 | Table 3, p. 6, row 27; `ORC-EZ77JD3VZ6` |  |
| 1473.15 | eutectoid: (βHf) -> CoHf2 + (αHf) | (βHf): Hf 0.96; CoHf2: Hf 0.74; (αHf): Hf 0.99 | experimental | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 26; `ORC-HX7R2VVRTA` |  |
| 923.15 | eutectoid: Co11Hf2 -> (αCo) + Co23Hf6 | Co11Hf2: Co 0.846154, Hf 0.153846; Co23Hf6: Co 0.793103, Hf 0.206897 | experimental | [1] Lu 2015; _cites Lu 2015_ [doi](https://doi.org/10.1016/j.jallcom.2014.11.206) | Table 3, p. 6, row 28; `ORC-PA4DI6ACBQ` |  |
| 923.15 | eutectoid: Co11Hf2 -> (αCo) + Co23Hf6 | Co11Hf2: Hf 0.1538; (αCo): Hf 0; Co23Hf6: Hf 0.2069 | model | [1] Lu 2015 | Table 3, p. 6, row 29; `ORC-SVQWU6DGXX` |  |
| 694.15 | eutectoid: (αCo) -> (εCo) + Co23Hf6 | (αCo): Hf 0; (εCo): Hf 0; Co23Hf6: Hf 0.2069 | model | [1] Lu 2015 | Table 3, p. 6, row 31; `ORC-235TZPEZVS` |  |
| 673.15 | eutectoid: (αCo) -> (εCo) + Co23Hf6 | (αCo): Hf 0.005; (εCo): Hf 0.004; Co23Hf6: Co 0.793103, Hf 0.206897 | model | [1] Lu 2015; _cites Svechnikov 1969_ | Table 3, p. 6, row 30; `ORC-BBEKWRTYHC` |  |

## 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–Hf system (8)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Co2Hf | [Co2Hf](https://data.orchid-project.org/compounds/Co2Hf.html) | -48 kJ/mol-atom | 298.15 | model | -35.622 (mp-aaaaadlx) | -36.917 (oqmd-1795641) | [2] Bratberg 2006 | Table 6, p. 5, row 15; `ORC-JAO7SGVJIH` |  |
| Co2Hf | [Co2Hf](https://data.orchid-project.org/compounds/Co2Hf.html) | -48 kJ/mol-atom | 298.15 | model | -35.622 (mp-aaaaadlx) | -36.917 (oqmd-1795641) | [2] Bratberg 2006; _cites Miedema 1998_ | Table 6, p. 5, row 14; `ORC-QJGQN6SFAQ` |  |
| Co2Hf | [Co2Hf](https://data.orchid-project.org/compounds/Co2Hf.html) | -39.4 kJ/mol-atom | 298.15 | experimental | -35.622 (mp-aaaaadlx) | -36.917 (oqmd-1795641) | [2] Bratberg 2006; _cites Binary 1986_ | Table 6, p. 5, row 13; `ORC-P3SQGPNU5N` |  |
| CoHf | [CoHf](https://data.orchid-project.org/compounds/CoHf.html) | -52 kJ/mol-atom | 298.15 | model | -38.703 (mp-aaacipkv) | -41.963 (oqmd-1375082) | [2] Bratberg 2006 | Table 6, p. 5, row 12; `ORC-LSAZDS65MQ` |  |
| CoHf | [CoHf](https://data.orchid-project.org/compounds/CoHf.html) | -51 kJ/mol-atom | 298.15 | model | -38.703 (mp-aaacipkv) | -41.963 (oqmd-1375082) | [2] Bratberg 2006; _cites Miedema 1998_ | Table 6, p. 5, row 11; `ORC-IJOXMXLLFY` |  |
| CoHf | [CoHf](https://data.orchid-project.org/compounds/CoHf.html) | -42.8 kJ/mol-atom | 298.15 | experimental | -38.703 (mp-aaacipkv) | -41.963 (oqmd-1375082) | [2] Bratberg 2006; _cites Binary 1986_ | Table 6, p. 5, row 10; `ORC-O6X5MU3NOA` |  |
| CoHf2 | [CoHf2](https://data.orchid-project.org/compounds/CoHf2.html) | -43 kJ/mol-atom | 298.15 | model | -28.174 (mp-aaacptpp) | -30.133 (oqmd-1365971) | [2] Bratberg 2006 | Table 6, p. 5, row 17; `ORC-EEXA43TSPZ` |  |
| CoHf2 | [CoHf2](https://data.orchid-project.org/compounds/CoHf2.html) | -38 kJ/mol-atom | 298.15 | model | -28.174 (mp-aaacptpp) | -30.133 (oqmd-1365971) | [2] Bratberg 2006; _cites Miedema 1998_ | Table 6, p. 5, row 16; `ORC-N5HZ3J43KZ` |  |

## Other properties

### Heat capacity / entropy / enthalpy (20)

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

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Heat content; _printed: Heat contents_ | 8.0099 kJ/mole atoms ± 0.29 | 586.85 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 11; `ORC-4ADSQHHIT7` |  |
| Heat content; _printed: Heat contents_ | 9.9867 kJ/mole atoms ± 2.32 | 587.75 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 1; `ORC-C3DSWWNC5F` |  |
| Heat content; _printed: Heat contents_ | 11.0297 kJ/mole atoms ± 0.34 | 688.91 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 2; `ORC-25IU2O276I` |  |
| Heat content; _printed: Heat contents_ | 10.7868 kJ/mole atoms ± 0.56 | 689.08 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 12; `ORC-B4IY4PDXNA` |  |
| Heat content; _printed: Heat contents_ | 13.9756 kJ/mole atoms ± 0.33 | 790.7 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 3; `ORC-U2VC3AZN4J` |  |
| Heat content; _printed: Heat contents_ | 13.7901 kJ/mole atoms ± 1.1 | 790.82 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 13; `ORC-RJIOMJYA4Q` |  |
| Heat content; _printed: Heat contents_ | 17.2277 kJ/mole atoms ± 0.22 | 891.83 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 4; `ORC-KTXDHHPZVG` |  |
| Heat content; _printed: Heat contents_ | 17.3985 kJ/mole atoms ± 1.81 | 892.09 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 14; `ORC-IYVLBY24P3` |  |
| Heat content; _printed: Heat contents_ | 19.7983 kJ/mole atoms ± 0.81 | 993.43 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 5; `ORC-NFLYKFAHAL` |  |
| Heat content; _printed: Heat contents_ | 19.8192 kJ/mole atoms ± 1.32 | 993.54 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 15; `ORC-TSR6EDN66I` |  |
| Heat content; _printed: Heat contents_ | 23.6661 kJ/mole atoms ± 1.32 | 1094.71 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 6; `ORC-DFBPUGMFWO` |  |
| Heat content; _printed: Heat contents_ | 22.2907 kJ/mole atoms ± 0.91 | 1094.94 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 16; `ORC-M42YJZ3SE7` |  |
| Heat content; _printed: Heat contents_ | 25.5361 kJ/mole atoms ± 1.21 | 1196.19 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 17; `ORC-3YND6GAMEY` |  |
| Heat content; _printed: Heat contents_ | 26.2749 kJ/mole atoms ± 0.89 | 1196.37 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 7; `ORC-CYLEFQ7KEU` |  |
| Heat content; _printed: Heat contents_ | 30.8695 kJ/mole atoms ± 3.44 | 1297.96 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 8; `ORC-MVP3W323X3` |  |
| Heat content; _printed: Heat contents_ | 31.5859 kJ/mole atoms ± 1.48 | 1298.01 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 18; `ORC-HSBQV5NPGV` |  |
| Heat content; _printed: Heat contents_ | 35.7274 kJ/mole atoms ± 2.61 | 1399.82 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 19; `ORC-R2POTK2OCV` |  |
| Heat content; _printed: Heat contents_ | 33.4084 kJ/mole atoms ± 1.04 | 1400.27 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 9; `ORC-LZ3J6SRLZF` |  |
| Heat content; _printed: Heat contents_ | 36.8657 kJ/mole atoms ± 1.52 | 1502.28 | CoHf2; _alloy: Hf 0.666667_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 20; `ORC-OLCEX5N5A5` |  |
| Heat content; _printed: Heat contents_ | 36.1185 kJ/mole atoms ± 1.88 | 1502.32 | Co2Hf; _alloy: Hf 0.333333_ | experimental | [1] Lu 2015 | Table 4, p. 8, row 10; `ORC-2FT4QM4G67` |  |

### Other property (1)

Table: Other property, Co–Hf system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Other; _printed: crystallization heat_ | 9 kJ/mole-atoms | 776.15 |  | experimental | [1] Lu 2015; _cites Jansson 1991_ [doi](https://doi.org/10.1016/0022-5088%2891%2990160-6) | p. 8; `ORC-EIY3LJLHEJ` | “Using the same methods, Jansson and Nygren \[8\] reported the Tx of a Co33Hf67 (at.%) alloy to be 503 C with a crystallization heat of 9.0 kJ/mole-atoms.” |

## Sources

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

1. Xingxu Lu, Shuhong Liu, Kaiming Cheng, Ying Tang, Pengfei Ou, Philip Nash et al., Thermodynamic modeling of the Co–Hf system supported by key experiments and first-principles calculations, Thermochimica Acta 608, 49-58 (2015). [doi:10.1016/j.tca.2015.04.004](https://doi.org/10.1016/j.tca.2015.04.004)
2. Johan Bratberg, Bo Jansson, Thermodynamic evaluation of the C−Co−W−Hf−Zr system for cemented carbides applications, JPED 27, 213-219 (2006). [doi:10.1361/154770306x109746](https://doi.org/10.1361/154770306x109746)

## 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/).