As–Fe phases

10 phases (tier A 7, liquid 2, needs_review 1); 9 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 · As–Fe system page · Markdown · field reference

Phases of the As–Fe system (10)
Phase	Structure	Basis	Stability (calculated)	TDB models
RHOMBOHEDRAL_A7 phase:as-fe:a7-rhombohedral	alpha-As · A7 · hR2 · R-3m (166)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1095.45 K, x(As) 1–1	2
BCC_A2 phase:as-fe:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–2499.68 K, x(As) 0–0.09849	2
FCC_A1 phase:as-fe:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 301.21–1789.82 K, x(As) 0–0.01503	2
FE2AS_C38 phase:as-fe:fe2as-c38	Cu2Sb · C38 · tP6 · P4/nmm (129)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1202.46 K, x(As) 0.33333–0.33333	2
FE3AS2 phase:as-fe:fe3as2		needs_review	stable in 2 of 2 calculated diagram(s): 1096.12–1249.91 K, x(As) 0.39708–0.42149	2
FEAS_B31 phase:as-fe:feas-b31	MnP · B31 · oP8 · Pnma (62)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1315.16 K, x(As) 0.5–0.5	2
FEAS2_C18 phase:as-fe:feas2-c18	alpha-FeS2 · C18 · oP6 · Pnnm (58)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1293.72 K, x(As) 0.66667–0.66667	2
HCP_A3 phase:as-fe:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
ION phase:as-fe:ion	liquid	liquid	stable in 1 of 1 calculated diagram(s): 1077.52–2500 K, x(As) 0–1	1
LIQUID phase:as-fe:liquid	liquid	liquid	stable in 1 of 1 calculated diagram(s): 1075.45–2500 K, x(As) 0–1	1

RHOMBOHEDRAL_A7 (As–Fe)

Id: phase:as-fe:a7-rhombohedral; status assigned
Structure: alpha-As · A7 · hR2 · R-3m (166); type st:a7-alpha-as-hr2; tier A: standard phase name; confidence high
Stoichiometry: As 1.0000
Stability: stable in 2 of 2 calculated diagram(s): 300–1095.45 K, x(As) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:a7-rhombohedral
tdb: tdb:FeAs-08Ohn.tdb:RHOMBOHEDRAL_A7, tdb:FeAs-94Pei-LB.tdb:RHOMBOHEDRAL_A7

TDB models of RHOMBOHEDRAL_A7 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: RHOMBOHEDRAL_A7, type code %, sha256 ed9f68c0b96e5b34…

46: PHASE RHOMBOHEDRAL_A7 % 1 1 !
47: CONST RHOMBOHEDRAL_A7 : AS : !

FeAs-94Pei-LB.tdb: RHOMBOHEDRAL_A7, type code %, sha256 24c905685b77bd98…

48: PHASE RHOMBOHEDRAL_A7 % 1 1 !
49: CONST RHOMBOHEDRAL_A7 : AS : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

BCC_A2 (As–Fe)

Id: phase:as-fe: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 2 of 2 calculated diagram(s): 300–2499.68 K, x(As) 0–0.09849
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:bcc-a2
tdb: tdb:FeAs-08Ohn.tdb:BCC_A2, tdb:FeAs-94Pei-LB.tdb:BCC_A2

TDB models of BCC_A2 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: BCC_A2, type code %B, sha256 ed9f68c0b96e5b34…

36: PHASE BCC_A2 %B 2 1 3 !
37: CONST BCC_A2 : AS FE% : VA : !

FeAs-94Pei-LB.tdb: BCC_A2, type code %B, sha256 24c905685b77bd98…

38: PHASE BCC_A2 %B 2 1 3 !
39: CONST BCC_A2 : AS FE% : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

FCC_A1 (As–Fe)

Id: phase:as-fe: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 2 of 2 calculated diagram(s): 301.21–1789.82 K, x(As) 0–0.01503
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:fcc-a1
tdb: tdb:FeAs-08Ohn.tdb:FCC_A1, tdb:FeAs-94Pei-LB.tdb:FCC_A1

TDB models of FCC_A1 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: FCC_A1, type code %A, sha256 ed9f68c0b96e5b34…

31: PHASE FCC_A1 %A 2 1 1 !
32: CONST FCC_A1 : AS FE% : VA : !

FeAs-94Pei-LB.tdb: FCC_A1, type code %A, sha256 24c905685b77bd98…

33: PHASE FCC_A1 %A 2 1 1 !
34: CONST FCC_A1 : AS FE% : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

FE2AS_C38 (As–Fe)

Id: phase:as-fe:fe2as-c38; status assigned
Structure: Cu2Sb · C38 · tP6 · P4/nmm (129); type st:c38-cu2sb-tp6; tier A: standard phase name; confidence high
Stoichiometry: As 0.3333, Fe 0.6667
Stability: stable in 2 of 2 calculated diagram(s): 300–1202.46 K, x(As) 0.33333–0.33333
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:fe2as-c38
tdb: tdb:FeAs-08Ohn.tdb:FE2AS_C38, tdb:FeAs-94Pei-LB.tdb:FE2AS_C38

TDB models of FE2AS_C38 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: FE2AS_C38, type code %, sha256 ed9f68c0b96e5b34…

51: PHASE FE2AS_C38 % 2 2 1 !
52: CONST FE2AS_C38 : FE : AS : !

FeAs-94Pei-LB.tdb: FE2AS_C38, type code %, sha256 24c905685b77bd98…

53: PHASE FE2AS_C38 % 2 2 1 !
54: CONST FE2AS_C38 : FE : AS : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

FE3AS2 (As–Fe)

Id: phase:as-fe:fe3as2; status needs_review
No structure assigned. Why: no_structure_token; off_stoichiometric_model; sgte_mmc2_row_incomplete
Candidate (sgte_mmc2): (Fe3As2) — Hallstedt 2025 mmc2 row for FE3AS2: Fe3As2
Stability: stable in 2 of 2 calculated diagram(s): 1096.12–1249.91 K, x(As) 0.39708–0.42149
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:fe3as2
tdb: tdb:FeAs-08Ohn.tdb:FE3AS2, tdb:FeAs-94Pei-LB.tdb:FE3AS2

TDB models of FE3AS2 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: FE3AS2, type code %, sha256 ed9f68c0b96e5b34…

56: PHASE FE3AS2 % 2 1 0.75 !
57: CONST FE3AS2 : FE : AS VA : !

FeAs-94Pei-LB.tdb: FE3AS2, type code %, sha256 24c905685b77bd98…

58: PHASE FE3AS2 % 2 1 0.75 !
59: CONST FE3AS2 : FE : AS VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

FEAS_B31 (As–Fe)

Id: phase:as-fe:feas-b31; status assigned
Structure: MnP · B31 · oP8 · Pnma (62); type st:b31-mnp-op8; tier A: standard phase name; confidence high
Stoichiometry: As 0.5000, Fe 0.5000
Stability: stable in 2 of 2 calculated diagram(s): 300–1315.16 K, x(As) 0.5–0.5
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:feas-b31
tdb: tdb:FeAs-08Ohn.tdb:FEAS_B31, tdb:FeAs-94Pei-LB.tdb:FEAS_B31

TDB models of FEAS_B31 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: FEAS_B31, type code %, sha256 ed9f68c0b96e5b34…

61: PHASE FEAS_B31 % 2 1 1 !
62: CONST FEAS_B31 : FE : AS : !

FeAs-94Pei-LB.tdb: FEAS_B31, type code %, sha256 24c905685b77bd98…

63: PHASE FEAS_B31 % 2 1 1 !
64: CONST FEAS_B31 : FE : AS : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

FEAS2_C18 (As–Fe)

Id: phase:as-fe:feas2-c18; status assigned
Structure: alpha-FeS2 · C18 · oP6 · Pnnm (58); type st:c18-alpha-fes2-op6; tier A: standard phase name; confidence high
Stoichiometry: As 0.6667, Fe 0.3333
Stability: stable in 2 of 2 calculated diagram(s): 300–1293.72 K, x(As) 0.66667–0.66667
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:feas2-c18
tdb: tdb:FeAs-08Ohn.tdb:FEAS2_C18, tdb:FeAs-94Pei-LB.tdb:FEAS2_C18

TDB models of FEAS2_C18 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: FEAS2_C18, type code %, sha256 ed9f68c0b96e5b34…

66: PHASE FEAS2_C18 % 2 1 2 !
67: CONST FEAS2_C18 : FE : AS : !

FeAs-94Pei-LB.tdb: FEAS2_C18, type code %, sha256 24c905685b77bd98…

68: PHASE FEAS2_C18 % 2 1 2 !
69: CONST FEAS2_C18 : FE : AS : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

HCP_A3 (As–Fe)

Id: phase:as-fe: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 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:as-fe:hcp-a3
tdb: tdb:FeAs-08Ohn.tdb:HCP_A3, tdb:FeAs-94Pei-LB.tdb:HCP_A3

TDB models of HCP_A3 (2): PHASE and CONSTITUENT statements as written

FeAs-08Ohn.tdb: HCP_A3, type code %A, sha256 ed9f68c0b96e5b34…

41: PHASE HCP_A3 %A 2 1 0.5 !
42: CONST HCP_A3 : AS FE : VA : !

FeAs-94Pei-LB.tdb: HCP_A3, type code %A, sha256 24c905685b77bd98…

43: PHASE HCP_A3 %A 2 1 0.5 !
44: CONST HCP_A3 : AS FE : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (2008).
assessment that models this phase
doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

ION (As–Fe)

Id: phase:as-fe:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 1077.52–2500 K, x(As) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:as-fe:ion
tdb: tdb:FeAs-94Pei-LB.tdb:ION

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

FeAs-94Pei-LB.tdb: ION, type code %, sha256 24c905685b77bd98…

28: PHASE ION:Y % 2 1 1 !
29: CONST ION:Y : FE+2 : AS-3 AS VA : !

Example references (1 of 1; assessments first):

doi:10.1515/ijmr-1994-850304 B. Pei, B. Bjoerkman, B. Jansson, B. Sundman, Z. Metallkd., 85, 171-77(1994).
assessment that models this phase

LIQUID (As–Fe)

Id: phase:as-fe:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 1075.45–2500 K, x(As) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:as-fe:liquid
tdb: tdb:FeAs-08Ohn.tdb:LIQUID

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

FeAs-08Ohn.tdb: LIQUID, type code %, sha256 ed9f68c0b96e5b34…

26: PHASE LIQUID:L % 1 1 !
27: CONST LIQUID:L : AS FE : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jcrysgro.2008.02.017 Munekazu Ohno, Kanji Yoh, Thermodynamic modeling of the system As–Fe combined with first-principles total energy calculations, Journal of Crystal Growth 310, 2751-2759 (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). 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}
}