# Fe–Ho system

> Fe–Ho system: 82 accepted literature values (phase transition 26, formation 22, invariant reaction 21, heat capacity / entropy / enthalpy 13) and 2 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

82 accepted literature values from 1 paper(s) (experimental 35, model 38, DFT 1, unspecified 8); 2 calculated phase diagram(s). 1 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/FE-HO.json) · [CSV](https://data.orchid-project.org/systems/FE-HO.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#FE-HO) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#FE-HO/FeHo-14Kar.json) · [phases (8)](https://data.orchid-project.org/phases/pages/FE-HO.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/FE-HO.html) · [Markdown](https://data.orchid-project.org/systems/FE-HO.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 35 |
| model | 38 |
| DFT | 1 |
| unspecified | 8 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 21 |
| phase transition | 26 |
| formation | 22 |
| heat capacity / entropy / enthalpy | 13 |

## 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 |
|---|---|---|---|
| FeHo-14Kar.tdb | S. Kardellas, C. Servant, N. Selhaoui, A. Iddaoudi, M. Ait Amar, L. Bouirden, J. Chem. Thermodyn., 74, 78-84(2014). [doi:10.1016/j.jct.2013.11.037](https://doi.org/10.1016/j.jct.2013.11.037) | `41fa95b081c454d800beac69d16cb74942c1cb8dbbd088d04594e23ee55cf8d6` | [viewer](https://orchid-project.org/phase-diagrams/#FE-HO/FeHo-14Kar.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/FeHo-14Kar.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/FeHo-14Kar.json) |
| FeHo-19Xu.tdb | L. Xu, J. Wang, S. Li, X.L. Chen, M.H. Rong, G.H. Rao, H.Y. Zhou, Calphad, 66, 101646(2019). [doi:10.1016/j.calphad.2019.101646](https://doi.org/10.1016/j.calphad.2019.101646) | `93b42acc4ccdb2f9878ecfe2e646c4cc8828fcfffb6258eda4e162548472e816` | [viewer](https://orchid-project.org/phase-diagrams/#FE-HO/FeHo-19Xu.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/FeHo-19Xu.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/FeHo-19Xu.json) |

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

| TDB file | T (K) | Phases at the invariant |
|---|---:|---|
| FeHo-14Kar.tdb | 1667.56 | BCC_A2 (x(Ho) 2.100e-4) + FCC_A1 (x(Ho) 2.100e-4) + LIQUID (x(Ho) 0.07064) |
| FeHo-14Kar.tdb | 1667.56 | FCC_A1 (x(Ho) 2.100e-4) + BCC_A2 (x(Ho) 2.100e-4) + LIQUID (x(Ho) 0.07064) |
| FeHo-14Kar.tdb | 1618.86 | FCC_A1 (x(Ho) 2.400e-4) + LIQUID (x(Ho) 0.09484) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-14Kar.tdb | 1618.86 | FCC_A1 (x(Ho) 2.400e-4) + LIQUID (x(Ho) 0.09474) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-14Kar.tdb | 1600.08 | FE17HO2 (x(Ho) 0.10526) + LIQUID (x(Ho) 0.16094) + FE23HO6_D8A (x(Ho) 0.2069) |
| FeHo-14Kar.tdb | 1600.08 | FE17HO2 (x(Ho) 0.10526) + LIQUID (x(Ho) 0.16084) + FE23HO6_D8A (x(Ho) 0.2069) |
| FeHo-14Kar.tdb | 1583.31 | FE23HO6_D8A (x(Ho) 0.2069) + FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.28507) |
| FeHo-14Kar.tdb | 1583.31 | FE23HO6_D8A (x(Ho) 0.2069) + FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.28537) |
| FeHo-14Kar.tdb | 1568.03 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.31781) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-14Kar.tdb | 1568.03 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.31773) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-14Kar.tdb | 1568.03 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.31823) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-14Kar.tdb | 1184.8 | FCC_A1 (x(Ho) 0) + BCC_A2 (x(Ho) 0) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-14Kar.tdb | 1151.93 | FE2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.63475) + HCP_A3 (x(Ho) 0.99423) |
| FeHo-14Kar.tdb | 1151.93 | FE2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.63488) + HCP_A3 (x(Ho) 0.99423) |
| FeHo-14Kar.tdb | 510.17 | FE17HO2 (x(Ho) 0.10526) + FE23HO6_D8A (x(Ho) 0.2069) + FE3HO (x(Ho) 0.25) |
| FeHo-14Kar.tdb | 344.65 | BCC_A2 (x(Ho) 0) + FE17HO2 (x(Ho) 0.10526) + FE3HO (x(Ho) 0.25) |
| FeHo-19Xu.tdb | 1667.47 | BCC_A2 (x(Ho) 3.000e-5) + FCC_A1 (x(Ho) 3.000e-5) + LIQUID (x(Ho) 0.06426) |
| FeHo-19Xu.tdb | 1667.47 | FCC_A1 (x(Ho) 3.000e-5) + BCC_A2 (x(Ho) 3.000e-5) + LIQUID (x(Ho) 0.06424) |
| FeHo-19Xu.tdb | 1612.23 | FCC_A1 (x(Ho) 3.000e-5) + LIQUID (x(Ho) 0.08691) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-19Xu.tdb | 1612.23 | FCC_A1 (x(Ho) 3.000e-5) + LIQUID (x(Ho) 0.08703) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-19Xu.tdb | 1591.04 | FE17HO2 (x(Ho) 0.10526) + LIQUID (x(Ho) 0.16148) + FE23HO6_D8A (x(Ho) 0.2069) |
| FeHo-19Xu.tdb | 1591.03 | FE17HO2 (x(Ho) 0.10526) + LIQUID (x(Ho) 0.16192) + FE23HO6_D8A (x(Ho) 0.2069) |
| FeHo-19Xu.tdb | 1572.06 | FE23HO6_D8A (x(Ho) 0.2069) + FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.283) |
| FeHo-19Xu.tdb | 1572.06 | FE23HO6_D8A (x(Ho) 0.2069) + FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.28266) |
| FeHo-19Xu.tdb | 1562.74 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.30308) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-19Xu.tdb | 1562.73 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.30275) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-19Xu.tdb | 1562.73 | FE3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.30263) + FE2HO_C15 (x(Ho) 0.33333) |
| FeHo-19Xu.tdb | 1184.81 | FCC_A1 (x(Ho) 0) + BCC_A2 (x(Ho) 0) + FE17HO2 (x(Ho) 0.10526) |
| FeHo-19Xu.tdb | 1153.4 | FE2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.63665) + HCP_A3 (x(Ho) 0.9946) |
| FeHo-19Xu.tdb | 1153.4 | FE2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.63667) + HCP_A3 (x(Ho) 0.9946) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/FE/FE-HO.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/FE/FE-HO.json) · [CALPHAD hull FeHo-14Kar](https://data.orchid-project.org/hulls/calphad-sgte/FE/FE-HO--FeHo-14Kar.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Fe–Ho system (21)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 1709.15 | (βHo) ↔ (αHo) + L |  | model | [1] Kardellass 2014 | Table 6, p. 4, row 29; `ORC-ILLRYK2OKA` |  |
| 1667.15 | δFe ↔ γFe + Liq |  | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 4; `ORC-TVITXGBM7Z` |  |
| 1662.15 | δFe ↔ γFe + Liq |  | model | [1] Kardellass 2014 | Table 6, p. 4, row 5; `ORC-JAWPDLEZRO` |  |
| 1612.15 | L ↔ γFe + Fe17Ho2 | Fe17Ho2: Ho 0.105263 | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 7; `ORC-AJS3S343HV` |  |
| 1611.15 | eutectic: L ↔ (γFe) + Fe17Ho2 | L: Ho 0.092; (γFe): Ho 0; Fe17Ho2: Ho 0.105 | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 4; `ORC-F5X6G7YCVN` |  |
| 1611.15 | L ↔ γFe + Fe17Ho2 | Fe17Ho2: Ho 0.105263 | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 6; `ORC-OZRACJDFFY` |  |
| 1591.15 | L ↔ Fe17Ho2 + Fe23Ho6 | Fe17Ho2: Ho 0.105263; Fe23Ho6: Ho 0.206897 | model | [1] Kardellass 2014 | Table 6, p. 4, row 15; `ORC-5E7WWDYXX4` |  |
| 1569.15 | L + Fe3Ho ↔ Fe23Ho6 | Fe3Ho: Ho 0.25; Fe23Ho6: Ho 0.206897 | model | [1] Kardellass 2014 | Table 6, p. 4, row 21; `ORC-GQBD22ECJO` |  |
| 1566.15 | peritectic: L + Fe23Ho6 ↔ Fe3Ho | L: Ho 0.27; Fe23Ho6: Ho 0.206; Fe3Ho: Ho 0.25 | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 8; `ORC-JEURT6MS5O` |  |
| 1566.15 | L + Fe3Ho ↔ Fe23Ho6 | Fe3Ho: Ho 0.25; Fe23Ho6: Ho 0.206897 | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 20; `ORC-TPLCF47LXI` |  |
| 1566.15 | L + Fe3Ho ↔ Fe23Ho6 | Fe3Ho: Ho 0.25; Fe23Ho6: Ho 0.206897 | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 19; `ORC-VEC7P2YRHK` |  |
| 1561.15 | L + Fe3Ho ↔ Fe2Ho | Fe3Ho: Ho 0.25; Fe2Ho: Ho 0.333333 | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 23; `ORC-FO6VWYJ24K` |  |
| 1561.15 | L + Fe3Ho ↔ Fe2Ho | Fe3Ho: Ho 0.25; Fe2Ho: Ho 0.333333 | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 22; `ORC-VTSBYXP42V` |  |
| 1558.15 | L ↔ Fe17Ho2 + Fe23Ho6 | Fe17Ho2: Ho 0.105263; Fe23Ho6: Ho 0.206897 | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 14; `ORC-CQUNH4WFME` |  |
| 1558.15 | L ↔ Fe17Ho2 + Fe23Ho6 | Fe17Ho2: Ho 0.105263; Fe23Ho6: Ho 0.206897 | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 13; `ORC-VD5EZG3JR3` |  |
| 1558.15 | peritectic: L + Fe3Ho ↔ Fe2Ho | L: Ho 0.36; Fe3Ho: Ho 0.25; Fe2Ho: Ho 0.333 | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 9; `ORC-XBETGO2HVS` |  |
| 1557.15 | eutectic: L ↔ Fe17Ho2 + Fe23Ho6 | L: Ho 0.178; Fe17Ho2: Ho 0.105; Fe23Ho6: Ho 0.206 | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 6; `ORC-P5H7MK3N4I` |  |
| 1554.15 | L + Fe3Ho ↔ Fe2Ho | Fe3Ho: Ho 0.25; Fe2Ho: Ho 0.333333 | model | [1] Kardellass 2014 | Table 6, p. 4, row 24; `ORC-Q2QEUVP5NR` |  |
| 1148.15 | L ↔ Fe2Ho + (αHo) | Fe2Ho: Ho 0.333333 | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 26; `ORC-HYZXR7DR2E` |  |
| 1148.15 | L ↔ Fe2Ho + (αHo) | Fe2Ho: Ho 0.333333 | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 27; `ORC-ZY5AXZSAKP` |  |
| 1146.15 | L ↔ Fe2Ho + (αHo) | Fe2Ho: Ho 0.333333 | model | [1] Kardellass 2014 | Table 6, p. 4, row 28; `ORC-2XMFWQ3RZA` |  |

## 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, Fe–Ho system (20)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Fe17Ho2 |  | -5.8 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 3; `ORC-AWBZOAR45I.96a337` |  |
| Fe17Ho2 |  | -4.32 kJ/mol (basis unstated) ± 0.02 | 1066 | experimental |  |  | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 2; `ORC-UIPG4H4SKB.b9fcbf` |  |
| Fe17Ho2 |  | -1.09 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Kardellass 2013_ | Table 3, p. 3, row 1; `ORC-ACOWIKVKUE.f7a0f5` |  |
| Fe17Ho2 |  | -0.295 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014 | Table 3, p. 3, row 4; `ORC-X2SWNTMAHM.c87067` |  |
| Fe23Ho6 |  | -6.7 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 7; `ORC-DZGZXMSEGH.5c7ba8` |  |
| Fe23Ho6 |  | -6.2 kJ/mol (basis unstated) | 300 | model |  |  | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 6; `ORC-WKYXXFHLRY.69285f` |  |
| Fe23Ho6 |  | -2.12 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Kardellass 2013_ | Table 3, p. 3, row 5; `ORC-5Z6DF3IBMI.d07e72` |  |
| Fe23Ho6 |  | -1.84 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014 | Table 3, p. 3, row 8; `ORC-QSWE2CZ6ZY.8fa8db` |  |
| Fe2Ho |  | -9.5 kJ/mol (basis unstated) | 298.15 | DFT |  |  | [1] Kardellass 2014; _cites Pauling_ | Table 3, p. 3, row 15; `ORC-J5ZAPW5P3R.623911` |  |
| Fe2Ho |  | -6.2 kJ/mol (basis unstated) | 300 | experimental |  |  | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 19; `ORC-O4O4JBXJXL.88ebbd` |  |
| Fe2Ho |  | -6.2 kJ/mol (basis unstated) | 300 | model |  |  | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 13; `ORC-VATGYD3ZK5.0981b4` |  |
| Fe2Ho |  | -5.9 kJ/mol (basis unstated) | 290 | experimental |  |  | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 18; `ORC-RV44IPUBUO.9c8eae` |  |
| Fe2Ho |  | -4.3 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [1] Kardellass 2014; _cites Latini 2013_ [doi](https://doi.org/10.1016/j.jct.2012.09.021) | Table 3, p. 3, row 14; `ORC-ZLQBKQ2PQ4.7e7a97` |  |
| Fe2Ho |  | -3 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Kardellass 2013_ | Table 3, p. 3, row 11; `ORC-42OZZ22NRH.9d2805` |  |
| Fe2Ho |  | -2.97 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Pauling_ | Table 3, p. 3, row 20; `ORC-FJUGJ2NCVS.e15efe` |  |
| Fe2Ho |  | -2.9 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Niessen 1983_ [doi](https://doi.org/10.1016/0364-5916%2883%2990030-5) | Table 3, p. 3, row 12; `ORC-KHGK7NMZJP.7769eb` |  |
| Fe2Ho |  | -2.65 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014 | Table 3, p. 3, row 17; `ORC-VUH3JZJG6S.85e37a` |  |
| Fe2Ho |  | -2.6 kJ/mol (basis unstated) ± 3.3 | 1373 | experimental |  |  | [1] Kardellass 2014; _cites Meschel 2013_ [doi](https://doi.org/10.1016/j.jallcom.2012.11.035) | Table 3, p. 3, row 16; `ORC-NHNYJN3TVX.65dd16` |  |
| Fe3Ho |  | -2.52 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014 | Table 3, p. 3, row 10; `ORC-7GTK6GP2WU.164376` |  |
| Fe3Ho |  | -2 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Kardellass 2014; _cites Kardellass 2013_ | Table 3, p. 3, row 9; `ORC-NXERYNGQOW.20f9e2` |  |

## Other properties

### Phase transition (26)

Table: Phase transition, Fe–Ho system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 325.15 K | 325.15 | magnetic | experimental | [1] Kardellass 2014; _cites Strnat 1966_ [doi](https://doi.org/10.1109/tmag.1966.1065874) | p. 3; `ORC-L74MZDD7JY` | “In good agreement, the Curie temperatures according to mutual induction measurements are 52 °C \[27\] for Fe17Ho2, 293 °C \[28\]” |
| Phase transition | 1185.15 K | 1185.15 | polymorphic | model | [1] Kardellass 2014; _cites Okamoto 1993_ | p. 1; `ORC-UR3J7O6UVA.fe8d8f` | “According to \[6,17\] the melting point of dFe is 1538 °C and the dFe M cFe and cFe M aFe allotropic transformation temperatures are 1394 °C and 912 °C, respectively.” |
| Phase transition | 1555.15 K | 1555.15 | L ↔ Fe2Ho; _L: Ho 0.333333; Fe2Ho: Ho 0.333333_ | model | [1] Kardellass 2014 | Table 6, p. 4, row 25; `ORC-Y32XRMLVPV` |  |
| Phase transition | 1561.15 K | 1561.15 | Fe2Ho | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | p. 1; `ORC-XQ2OYTTAHF.5a5428` | “The two phases Fe23Ho6 and Fe17Ho2 melted congruently at 1332 °C and 1343 °C, respectively, while Fe3Ho and Fe2Ho melted incongruently at 1293 °C and 1288 °C, respectively, table 1. The melting points for all the intermediate phases are believed accurate with ± 3 °C \[4\].” |
| Phase transition | 1566.15 K | 1566.15 | Fe3Ho | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | p. 1; `ORC-XQ2OYTTAHF.07316b` | “The two phases Fe23Ho6 and Fe17Ho2 melted congruently at 1332 °C and 1343 °C, respectively, while Fe3Ho and Fe2Ho melted incongruently at 1293 °C and 1288 °C, respectively, table 1. The melting points for all the intermediate phases are believed accurate with ± 3 °C \[4\].” |
| Phase transition | 1603.15 K | 1603.15 | L ↔ Fe23Ho6; _L: Ho 0.206897; Fe23Ho6: Ho 0.206897_ | model | [1] Kardellass 2014 | Table 6, p. 4, row 18; `ORC-H7N5YUWJER` |  |
| Phase transition | 1604.15 K | 1604.15 | L ↔ Fe23Ho6; _L: Ho 0.206897; Fe23Ho6: Ho 0.206897_ | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 17; `ORC-43XKR47NR2` |  |
| Phase transition | 1605.15 K | 1605.15 | L ↔ Fe23Ho6; _L: Ho 0.206897; Fe23Ho6: Ho 0.206897_ | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 16; `ORC-CERHVLGIHO` |  |
| Phase transition | 1605.15 K | 1605.15 | congruent melting | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | p. 1; `ORC-XQ2OYTTAHF.be0e2c` | “The two phases Fe23Ho6 and Fe17Ho2 melted congruently at 1332 °C and 1343 °C, respectively, while Fe3Ho and Fe2Ho melted incongruently at 1293 °C and 1288 °C, respectively, table 1. The melting points for all the intermediate phases are believed accurate with ± 3 °C \[4\].” |
| Phase transition | 1605.15 K | 1605.15 | congruent melting: L ↔ Fe23Ho6; _L: Ho 0.206; Fe23Ho6: Ho 0.206_ | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 7; `ORC-I22REOXZDR` |  |
| Phase transition | 1613.15 K | 1613.15 | L ↔ Fe17Ho2; _L: Ho 0.105263; Fe17Ho2: Ho 0.105263_ | model | [1] Kardellass 2014 | Table 6, p. 4, row 12; `ORC-3VFDKYWRRZ` |  |
| Phase transition | 1616.15 K | 1616.15 | L ↔ Fe17Ho2; _L: Ho 0.105263; Fe17Ho2: Ho 0.105263_ | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 10; `ORC-UPPWOGHNGH` |  |
| Phase transition | 1616.15 K | 1616.15 | congruent melting | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | p. 1; `ORC-XQ2OYTTAHF.a37ce0` | “The two phases Fe23Ho6 and Fe17Ho2 melted congruently at 1332 °C and 1343 °C, respectively, while Fe3Ho and Fe2Ho melted incongruently at 1293 °C and 1288 °C, respectively, table 1. The melting points for all the intermediate phases are believed accurate with ± 3 °C \[4\].” |
| Phase transition | 1616.15 K | 1616.15 | congruent melting: L ↔ Fe17Ho2; _L: Ho 0.105; Fe17Ho2: Ho 0.105_ | unspecified | [1] Kardellass 2014; _cites Okamoto 1993_ | Table 1, p. 2, row 5; `ORC-Q5VTOXKHEM` |  |
| Phase transition | 1617.15 K | 1617.15 | L ↔ Fe17Ho2; _L: Ho 0.105263; Fe17Ho2: Ho 0.105263_ | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 11; `ORC-JIYT77VSUL` |  |
| Phase transition | 1667.15 K | 1667.15 | polymorphic | model | [1] Kardellass 2014; _cites Okamoto 1993_ | p. 1; `ORC-UR3J7O6UVA.e399d0` | “According to \[6,17\] the melting point of dFe is 1538 °C and the dFe M cFe and cFe M aFe allotropic transformation temperatures are 1394 °C and 912 °C, respectively.” |
| Phase transition | 1744.15 K | 1744.15 | L ↔ (βHo) | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 31; `ORC-S2MIBE6CVO` |  |
| Phase transition | 1745.15 K | 1745.15 | congruent melting: L ↔ (βHo); _(βHo): Ho 1_ | unspecified | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 1, p. 2, row 11; `ORC-TCLCNJTBOH` |  |
| Phase transition | 1747.15 K | 1747.15 | Ho + liquid | model | [1] Kardellass 2014; _cites Massalski 1991_ | p. 2; `ORC-UKD22EY4TR` | “The melting point of Ho is 1474 °C \[17\].” |
| Phase transition | 1747.15 K | 1747.15 | L ↔ (βHo) | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 30; `ORC-CHW6AIWNP4` |  |
| Phase transition | 1747.15 K | 1747.15 | L ↔ (βHo) | model | [1] Kardellass 2014 | Table 6, p. 4, row 32; `ORC-MBV2WL4F5F` |  |
| Phase transition | 1809.15 K | 1809.15 | δFe ↔ Liq | experimental | [1] Kardellass 2014; _cites Roe 1970_ [doi](https://doi.org/10.1007/bf03038385) | Table 6, p. 4, row 2; `ORC-UHUXDRBI7M` |  |
| Phase transition | 1811.15 K | 1811.15 | congruent melting: L ↔ δFe; _δFe: Ho 0_ | unspecified | [1] Kardellass 2014; _cites Massalski 1991_ | Table 1, p. 2, row 1; `ORC-2RA2MPVS5H` |  |
| Phase transition | 1811.15 K | 1811.15 | dFe + liquid | model | [1] Kardellass 2014; _cites Okamoto 1993_ | p. 1; `ORC-UR3J7O6UVA.fb4e78` | “According to \[6,17\] the melting point of dFe is 1538 °C and the dFe M cFe and cFe M aFe allotropic transformation temperatures are 1394 °C and 912 °C, respectively.” |
| Phase transition | 1811.15 K | 1811.15 | δFe ↔ Liq | model | [1] Kardellass 2014 | Table 6, p. 4, row 3; `ORC-5K7EDU2EW2` |  |
| Phase transition | 1811.15 K | 1811.15 | δFe ↔ Liq | experimental | [1] Kardellass 2014; _cites Kubaschewski 1982_ | Table 6, p. 4, row 1; `ORC-NVPKNDIZZY` |  |

### Formation (2)

Table: Formation, Fe–Ho system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy of formation | 1.8 J/mol (basis unstated)/K | 298.15 | Fe17Ho2; _alloy: Ho 0.105263_ | model | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 3; `ORC-AWBZOAR45I.04c0ca` |  |
| Entropy of formation | 0.85 J/mol (basis unstated)/K ± 0.01 | 1066 | Fe17Ho2; _alloy: Ho 0.105263_ | experimental | [1] Kardellass 2014; _cites Gozzi 2007_ [doi](https://doi.org/10.1021/je7003353) | Table 3, p. 3, row 2; `ORC-UIPG4H4SKB.31fda0` |  |

### Heat capacity / entropy / enthalpy (13)

Table: Heat capacity / entropy / enthalpy, Fe–Ho system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: Entropy of formation_ | 41.63 J/mol (basis unstated)/K | 290 | Fe2Ho; _alloy: Ho 0.333333_ | experimental | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 18; `ORC-RV44IPUBUO.694280` |  |
| Entropy; _printed: Entropy of formation_ | 38.03 J/mol (basis unstated)/K | 298.15 | Fe17Ho2; _alloy: Ho 0.105263_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 4; `ORC-X2SWNTMAHM.58fe1f` |  |
| Entropy; _printed: Entropy of formation_ | 43.15 J/mol (basis unstated)/K | 298.15 | Fe23Ho6; _alloy: Ho 0.206897_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 8; `ORC-QSWE2CZ6ZY.70e2aa` |  |
| Entropy; _printed: Entropy of formation_ | 49.18 J/mol (basis unstated)/K | 298.15 | Fe2Ho; _alloy: Ho 0.333333_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 17; `ORC-VUH3JZJG6S.629c33` |  |
| Entropy; _printed: Entropy of formation_ | 45.02 J/mol (basis unstated)/K | 298.15 | Fe3Ho; _alloy: Ho 0.25_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 10; `ORC-7GTK6GP2WU.9376e3` |  |
| Entropy; _printed: Entropy of formation_ | 42.66 J/mol (basis unstated)/K | 300 | Fe2Ho; _alloy: Ho 0.333333_ | experimental | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 19; `ORC-O4O4JBXJXL.c0b072` |  |
| Entropy; _printed: Entropy of formation_ | 42.66 J/mol (basis unstated)/K | 300 | Fe2Ho; _alloy: Ho 0.333333_ | model | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 13; `ORC-VATGYD3ZK5.bbf17c` |  |
| Heat capacity | 30.09 J/mol (basis unstated)/K | 290 | Fe2Ho; _alloy: Ho 0.333333_ | experimental | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 18; `ORC-RV44IPUBUO.32961b` |  |
| Heat capacity | 24.71 J/mol (basis unstated)/K | 298.15 | Fe17Ho2; _alloy: Ho 0.105263_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 4; `ORC-X2SWNTMAHM.fdb434` |  |
| Heat capacity | 24.98 J/mol (basis unstated)/K | 298.15 | Fe23Ho6; _alloy: Ho 0.206897_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 8; `ORC-QSWE2CZ6ZY.6cf63f` |  |
| Heat capacity | 25.33 J/mol (basis unstated)/K | 298.15 | Fe2Ho; _alloy: Ho 0.333333_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 17; `ORC-VUH3JZJG6S.751e44` |  |
| Heat capacity | 25.11 J/mol (basis unstated)/K | 298.15 | Fe3Ho; _alloy: Ho 0.25_ | model | [1] Kardellass 2014 | Table 3, p. 3, row 10; `ORC-7GTK6GP2WU.b9726c` |  |
| Heat capacity | 30.45 J/mol (basis unstated)/K | 300 | Fe2Ho; _alloy: Ho 0.333333_ | experimental | [1] Kardellass 2014; _cites Germano 1981_ [doi](https://doi.org/10.1016/0022-4596%2881%2990500-4) | Table 3, p. 3, row 19; `ORC-O4O4JBXJXL.524bc5` |  |

## Sources

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

1. S. Kardellass, C. Servant, N. Selhaoui, A. Iddaoudi, M. Ait Amar, L. Bouirden, A thermodynamic assessment of the Iron+Holmium phase diagram, The Journal of Chemical Thermodynamics 74, 78-84 (2014). [doi:10.1016/j.jct.2013.11.037](https://doi.org/10.1016/j.jct.2013.11.037)

## 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/).