Fe–H phases

6 phases (tier A 3, liquid 1, gas 2); 5 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 · full JSON · Fe–H system page · Markdown · field reference

Phases of the Fe–H system (6)
Phase	Structure	Basis	Stability (calculated)	TDB models
BCC_A2 phase:fe-h:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–1810 K, x(H) 0–0.00063	1
FCC_A1 phase:fe-h:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 1183.88–1669.27 K, x(H) 0–0.00048	1
GAS phase:fe-h:gas	gas	gas	stable in 1 of 1 calculated diagram(s): 300–2500 K, x(H) 0.98282–1	1
H2GAS phase:fe-h:h2gas	gas	gas	stable in 1 of 1 calculated diagram(s): 301.13–1092.38 K, x(H) 1–1	1
HCP_A3 phase:fe-h:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 1 calculated diagram(s)	1
LIQUID phase:fe-h:liquid	liquid	liquid	stable in 1 of 1 calculated diagram(s): 1809.72–2500 K, x(H) 0–0.00203	1

BCC_A2 (Fe–H)

Id: phase:fe-h: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): 300–1810 K, x(H) 0–0.00063
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:bcc-a2
tdb: tdb:FeH-02Zin.tdb:BCC_A2

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

FeH-02Zin.tdb: BCC_A2, type code %B, sha256 46c9a090cddbabe8…

44: PHASE BCC_A2 %B 2 1 1 !
45: CONST BCC_A2 : FE : H VA% : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
assessment that models this phase

FCC_A1 (Fe–H)

Id: phase:fe-h: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): 1183.88–1669.27 K, x(H) 0–0.00048
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:fcc-a1
tdb: tdb:FeH-02Zin.tdb:FCC_A1

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

FeH-02Zin.tdb: FCC_A1, type code %A, sha256 46c9a090cddbabe8…

38: PHASE FCC_A1 %A 2 1 1 !
39: CONST FCC_A1 : FE : H VA% : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
assessment that models this phase

GAS (Fe–H)

Id: phase:fe-h:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 300–2500 K, x(H) 0.98282–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:gas
tdb: tdb:FeH-02Zin.tdb:GAS

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

FeH-02Zin.tdb: GAS, type code %, sha256 46c9a090cddbabe8…

52: PHASE GAS:G % 1 1 !
53: CONST GAS:G : FE FE2 FEH H H2 : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
assessment that models this phase

H2GAS (Fe–H)

Id: phase:fe-h:h2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 301.13–1092.38 K, x(H) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:h2gas
tdb: tdb:FeH-02Zin.tdb:H2GAS

TDB models of H2GAS (1): PHASE and CONSTITUENT statements as written

FeH-02Zin.tdb: H2GAS, type code %, sha256 46c9a090cddbabe8…

55: PHASE H2GAS % 1 1 !
56: CONST H2GAS : H2 : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
assessment that models this phase

HCP_A3 (Fe–H)

Id: phase:fe-h: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: not stable in 1 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:hcp-a3
tdb: tdb:FeH-02Zin.tdb:HCP_A3

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

FeH-02Zin.tdb: HCP_A3, type code %A, sha256 46c9a090cddbabe8…

49: PHASE HCP_A3 %A 2 1 0.5 !
50: CONST HCP_A3 : FE : H VA% : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
assessment that models this phase

LIQUID (Fe–H)

Id: phase:fe-h:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 1809.72–2500 K, x(H) 0–0.00203
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:fe-h:liquid
tdb: tdb:FeH-02Zin.tdb:LIQUID

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

FeH-02Zin.tdb: LIQUID, type code %, sha256 46c9a090cddbabe8…

33: PHASE LIQUID:L % 1 1 !
34: CONST LIQUID:L : FE H : !

Example references (1 of 1; assessments first):

doi:10.1016/S0925-8388(01)01990-9 M. Zinkevich, N. Mattern, A. Handstein, O. Gutfleisch, J. Alloys Compd., 339, 118-139(2002).
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). doi: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). doi: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.

@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}
}