# Fe–Hf phases

> Fe–Hf system: 8 phases (tier A 6, tier C 1, liquid 1); 8 stable in a calculated diagram in the ORCHID phase registry, with names, structure type when the stored evidence supports an assignment under the stated tier rules, calculated stability, verbatim TDB PHASE/CONSTITUENT statements and example references.

HTML: https://data.orchid-project.org/phases/pages/FE-HF.html · Markdown: https://data.orchid-project.org/phases/pages/FE-HF.md

8 phases (tier A 6, tier C 1, liquid 1); 8 stable in a calculated diagram. Structure types are assigned only when the stored evidence supports an assignment under the stated tier rules (tier A: standard phase name; tier B: unique Materials Project + OQMD on-hull match, DFT-supported; tier C: one structure stated by the assessment's crystallographic table, assessor-stated); other phases list candidates and are marked needs_review. Stability is from phase diagrams calculated with pycalphad from the SGTE binary collection (evidence class: model).

Data: [interactive registry](https://orchid-project.org/phases/?q=FE-HF) · [full JSON](https://data.orchid-project.org/phases/systems/FE-HF.json) · [Fe–Hf system page](https://data.orchid-project.org/systems/FE-HF.html) · [Markdown](https://data.orchid-project.org/phases/pages/FE-HF.md) · [field reference](https://data.orchid-project.org/phases/SCHEMA.md)

Table: Phases of the Fe–Hf system (8)

| Phase | Structure | Basis | Stability (calculated) | Literature values | TDB models |
|---|---|---|---|---:|---:|
| [BCC_A2](#phase-fe-hf-bcc-a2); _phase:fe-hf:bcc-a2_ | W · A2 · cI2 · Im-3m (229) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–3999.8 K, x(Hf) 0–1 | 0 | 1 |
| [FCC_A1](#phase-fe-hf-fcc-a1); _phase:fe-hf:fcc-a1_ | Cu · A1 · cF4 · Fm-3m (225) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 1159.9–1722.59 K, x(Hf) 0–0.00018 | 0 | 1 |
| [FE2HF_C14](#phase-fe-hf-fe2hf-c14); _phase:fe-hf:fe2hf-c14_ | MgZn2 · C14 · hP12 · P6_3/mmc (194) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–2091.22 K, x(Hf) 0.24299–0.31962 | 0 | 1 |
| [FE2HF_C15](#phase-fe-hf-fe2hf-c15); _phase:fe-hf:fe2hf-c15_ | Cu2Mg · C15 · cF24 · Fd-3m (227) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–1474.54 K, x(Hf) 0.33333–0.33333 | 0 | 1 |
| [FE2HF_C36](#phase-fe-hf-fe2hf-c36); _phase:fe-hf:fe2hf-c36_ | MgNi2 · C36 · hP24 · P6_3/mmc (194) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 1474.54–1933.37 K, x(Hf) 0.33333–0.33333 | 0 | 1 |
| [FEHF2](#phase-fe-hf-fehf2); _phase:fe-hf:fehf2_ | NiTi2 · cF96 · Fd-3m (227) | tier C: assessor-stated (Hallstedt 2025 crystallographic table) | stable in 1 of 1 calculated diagram(s): 300–1531.26 K, x(Hf) 0.66667–0.66667 | 8 | 1 |
| [HCP_A3](#phase-fe-hf-hcp-a3); _phase:fe-hf:hcp-a3_ | Mg · A3 · hP2 · P6_3/mmc (194) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–2503.56 K, x(Hf) 1–1 | 0 | 1 |
| [LIQUID](#phase-fe-hf-liquid); _phase:fe-hf:liquid_ | liquid | liquid | stable in 1 of 1 calculated diagram(s): 1573.55–4000 K, x(Hf) 0–1 | 0 | 1 |

## BCC_A2 (Fe–Hf)

- Id: `phase:fe-hf:bcc-a2`; status `assigned`
- Structure: W · A2 · cI2 · Im-3m (229); type `st:a2-w-ci2`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 300–3999.8 K, x(Hf) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:bcc-a2)

Names (2): _corpus: _corpus:phase:fe-hf:bcc-a2  
_tdb: _tdb:FeHf-08Idb.tdb:BCC_A2  


### TDB models of BCC_A2 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): BCC_A2, type code %B, sha256 `2a85ddea9bbae84b…`

~~~~text
40: PHASE BCC_A2 %B 2 1 3 !
41: CONST BCC_A2 : FE% HF% : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## FCC_A1 (Fe–Hf)

- Id: `phase:fe-hf:fcc-a1`; status `assigned`
- Structure: Cu · A1 · cF4 · Fm-3m (225); type `st:a1-cu-cf4`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 1159.9–1722.59 K, x(Hf) 0–0.00018
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:fcc-a1)

Names (2): _corpus: _corpus:phase:fe-hf:fcc-a1  
_tdb: _tdb:FeHf-08Idb.tdb:FCC_A1  


### TDB models of FCC_A1 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): FCC_A1, type code %A, sha256 `2a85ddea9bbae84b…`

~~~~text
35: PHASE FCC_A1 %A 2 1 1 !
36: CONST FCC_A1 : FE% HF : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## FE2HF_C14 (Fe–Hf)

- Id: `phase:fe-hf:fe2hf-c14`; status `assigned`
- Structure: MgZn2 · C14 · hP12 · P6_3/mmc (194); type `st:c14-mgzn2-hp12`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 300–2091.22 K, x(Hf) 0.24299–0.31962
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:fe2hf-c14)

Names (2): _corpus: _corpus:phase:fe-hf:fe2hf-c14  
_tdb: _tdb:FeHf-08Idb.tdb:FE2HF_C14  


### TDB models of FE2HF_C14 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): FE2HF_C14, type code %, sha256 `2a85ddea9bbae84b…`

~~~~text
50: PHASE FE2HF_C14 % 2 2 1 !
51: CONST FE2HF_C14 : FE : FE HF% : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## FE2HF_C15 (Fe–Hf)

- Id: `phase:fe-hf:fe2hf-c15`; status `assigned`
- Structure: Cu2Mg · C15 · cF24 · Fd-3m (227); type `st:c15-cu2mg-cf24`; tier A: standard phase name; confidence high
- Stoichiometry: Fe 0.6667, Hf 0.3333
- Stability: stable in 1 of 1 calculated diagram(s): 300–1474.54 K, x(Hf) 0.33333–0.33333
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:fe2hf-c15)

Names (2): _corpus: _corpus:phase:fe-hf:fe2hf-c15  
_tdb: _tdb:FeHf-08Idb.tdb:FE2HF_C15  


### TDB models of FE2HF_C15 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): FE2HF_C15, type code %, sha256 `2a85ddea9bbae84b…`

~~~~text
55: PHASE FE2HF_C15 % 2 2 1 !
56: CONST FE2HF_C15 : FE : HF : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## FE2HF_C36 (Fe–Hf)

- Id: `phase:fe-hf:fe2hf-c36`; status `assigned`
- Structure: MgNi2 · C36 · hP24 · P6_3/mmc (194); type `st:c36-mgni2-hp24`; tier A: standard phase name; confidence high
- Stoichiometry: Fe 0.6667, Hf 0.3333
- Stability: stable in 1 of 1 calculated diagram(s): 1474.54–1933.37 K, x(Hf) 0.33333–0.33333
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:fe2hf-c36)

Names (2): _corpus: _corpus:phase:fe-hf:fe2hf-c36  
_tdb: _tdb:FeHf-08Idb.tdb:FE2HF_C36  


### TDB models of FE2HF_C36 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): FE2HF_C36, type code %, sha256 `2a85ddea9bbae84b…`

~~~~text
60: PHASE FE2HF_C36 % 2 2 1 !
61: CONST FE2HF_C36 : FE : HF : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## FEHF2 (Fe–Hf)

- Id: `phase:fe-hf:fehf2`; status `assigned`
- Structure: NiTi2 · cF96 · Fd-3m (227); type `st:niti2-cf96`; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
- Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) [doi:10.1016/j.calphad.2025.102833](https://doi.org/10.1016/j.calphad.2025.102833)
- Caveat: not certain from the name or DFT alone (no_on_hull_entry_in_oqmd, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
- Stoichiometry: Fe 0.3333, Hf 0.6667
- Stability: stable in 1 of 1 calculated diagram(s): 300–1531.26 K, x(Hf) 0.66667–0.66667
- Literature: 8 values (8 accepted) from 1 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:fehf2)

Names (4): _corpus: _corpus:phase:fe-hf:fehf2  
_paper: _paper:10.1016/j.jallcom.2007.02.036:FeHF2, paper:10.1016/j.jallcom.2007.02.036:FeHf2  
_tdb: _tdb:FeHf-08Idb.tdb:FEHF2  


### TDB models of FEHF2 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): FEHF2, type code %, sha256 `2a85ddea9bbae84b…`

~~~~text
65: PHASE FEHF2 % 2 1 2 !
66: CONST FEHF2 : FE : HF : !
~~~~

Example references (4 of 4; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase; reports values for this phase_
- [doi:10.1007/bf02665763](https://doi.org/10.1007/bf02665763) J. C. Gachon, N. Selhaoui, B. Aba, J. Hertz, Comparison between measured and predicted enthalpies of formation, JPE 13, 506-511 (1992).  
_cited as the source of values for this phase_
- [doi:10.1016/0364-5916(83)90030-5](https://doi.org/10.1016/0364-5916%2883%2990030-5) A.K. Niessen, F.R. de Boer, R. Boom, P.F. de Chatel, W.C.M. Mattens, A.R. Miedema, CALPHAD 7 (1983) 51–70.  
_cited as the source of values for this phase_
- [doi:10.1016/0364-5916(85)90032-x](https://doi.org/10.1016/0364-5916%2885%2990032-x) C. Colinet, A. Pasturel, P. Hicter, Calphad 9 (1985) 71–99.  
_cited as the source of values for this phase_

## HCP_A3 (Fe–Hf)

- Id: `phase:fe-hf:hcp-a3`; status `assigned`
- Structure: Mg · A3 · hP2 · P6_3/mmc (194); type `st:a3-mg-hp2`; tier A: standard phase name; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 300–2503.56 K, x(Hf) 1–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:hcp-a3)

Names (2): _corpus: _corpus:phase:fe-hf:hcp-a3  
_tdb: _tdb:FeHf-08Idb.tdb:HCP_A3  


### TDB models of HCP_A3 (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): HCP_A3, type code %A, sha256 `2a85ddea9bbae84b…`

~~~~text
45: PHASE HCP_A3 %A 2 1 0.5 !
46: CONST HCP_A3 : FE HF% : VA : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## LIQUID (Fe–Hf)

- Id: `phase:fe-hf:liquid`; status `assigned`
- Structure: liquid; type `st:liquid`; liquid; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 1573.55–4000 K, x(Hf) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:fe-hf:liquid)

Names (2): _corpus: _corpus:phase:fe-hf:liquid  
_tdb: _tdb:FeHf-08Idb.tdb:LIQUID  


### TDB models of LIQUID (1): PHASE and CONSTITUENT statements as written

[FeHf-08Idb.tdb](https://orchid-project.org/data/databases/sgte-binary/FeHf-08Idb.tdb): LIQUID, type code %, sha256 `2a85ddea9bbae84b…`

~~~~text
30: PHASE LIQUID:L % 1 1 !
31: CONST LIQUID:L : FE HF : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/j.jallcom.2007.02.036](https://doi.org/10.1016/j.jallcom.2007.02.036) M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008).  
_assessment that models this phase_

## Please cite

- R. Arróyave, J. Saal, D. Shin, ORCHID-Registry: phase registry of binary systems (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23735970
- 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 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); the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work).

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_phase_registry_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Registry: phase registry of binary systems}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735970},
  url       = {https://doi.org/10.5281/zenodo.23735970},
  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 the ORCHID phase registry and the sources named on the page (TDB assessments, Hallstedt 2025, Materials Project, OQMD). TDB statements are quoted as written; parameter expressions are not reproduced. Field reference: [SCHEMA.md](https://data.orchid-project.org/phases/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt).