Ni–O phases

8 phases (tier A 4, liquid 2, gas 2); 6 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 · Ni–O system page · Markdown · field reference

Phases of the Ni–O system (8)
Phase	Structure	Basis	Stability (calculated)	TDB models
OXIDE_B1 phase:ni-o:b1-oxide	NaCl · B1 · cF8 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–2235.77 K, x(O) 0.5–0.50187	2
BCC_A2 phase:ni-o:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
FCC_A1 phase:ni-o:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1728.25 K, x(O) 0–0.00171	2
GAS phase:ni-o:gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300.46–2500 K, x(O) 0.99217–1	2
HCP_A3 phase:ni-o:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
ION phase:ni-o:ion	liquid	liquid	stable in 2 of 2 calculated diagram(s): 1714.17–2500 K, x(O) 0–0.49912	2
LIQUID phase:ni-o:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 1720–2500 K, x(O) 0–0.49	2
O2GAS phase:ni-o:o2gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–1620 K, x(O) 1–1	2

OXIDE_B1 (Ni–O)

Id: phase:ni-o:b1-oxide; status assigned
Structure: NaCl · B1 · cF8 · Fm-3m (225); type st:b1-nacl-cf8; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–2235.77 K, x(O) 0.5–0.50187
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:b1-oxide
tdb: tdb:NiO-90Tay.tdb:OXIDE_B1, tdb:NiO-95Kow.tdb:OXIDE_B1

TDB models of OXIDE_B1 (2): PHASE and CONSTITUENT statements as written

NiO-90Tay.tdb: OXIDE_B1, type code %C, sha256 a612d67283e61479…

53: PHASE OXIDE_B1:I %C 2 1 1 !
54: CONST OXIDE_B1:I : NI+2% NI+3 VA : O-2 : !

NiO-95Kow.tdb: OXIDE_B1, type code %C, sha256 a7d68a7866eed0eb…

55: PHASE OXIDE_B1:I %C 2 1 1 !
56: CONST OXIDE_B1:I : NI+2% NI+3 VA : O-2 : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

BCC_A2 (Ni–O)

Id: phase:ni-o:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; 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:ni-o:bcc-a2
tdb: tdb:NiO-90Tay.tdb:BCC_A2, tdb:NiO-95Kow.tdb:BCC_A2

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

NiO-90Tay.tdb: BCC_A2, type code %B, sha256 a612d67283e61479…

43: PHASE BCC_A2 %B 2 1 3 !
44: CONST BCC_A2 : NI : VA : !

NiO-95Kow.tdb: BCC_A2, type code %B, sha256 a7d68a7866eed0eb…

45: PHASE BCC_A2 %B 2 1 3 !
46: CONST BCC_A2 : NI : O VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

FCC_A1 (Ni–O)

Id: phase:ni-o: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): 300–1728.25 K, x(O) 0–0.00171
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:fcc-a1
tdb: tdb:NiO-90Tay.tdb:FCC_A1, tdb:NiO-95Kow.tdb:FCC_A1

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

NiO-90Tay.tdb: FCC_A1, type code %A, sha256 a612d67283e61479…

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

NiO-95Kow.tdb: FCC_A1, type code %A, sha256 a7d68a7866eed0eb…

40: PHASE FCC_A1 %A 2 1 1 !
41: CONST FCC_A1 : NI : O VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

GAS (Ni–O)

Id: phase:ni-o:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300.46–2500 K, x(O) 0.99217–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:gas
tdb: tdb:NiO-90Tay.tdb:GAS, tdb:NiO-95Kow.tdb:GAS

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

NiO-90Tay.tdb: GAS, type code %, sha256 a612d67283e61479…

56: PHASE GAS:G % 1 1 !
57: CONST GAS:G : NI NI2 NIO O O2% O3 : !

NiO-95Kow.tdb: GAS, type code %, sha256 a7d68a7866eed0eb…

58: PHASE GAS:G % 1 1 !
59: CONST GAS:G : NI NI2 NIO O O2% O3 : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

HCP_A3 (Ni–O)

Id: phase:ni-o:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
Stoichiometry: Ni 1.0000
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:ni-o:hcp-a3
tdb: tdb:NiO-90Tay.tdb:HCP_A3, tdb:NiO-95Kow.tdb:HCP_A3

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

NiO-90Tay.tdb: HCP_A3, type code %A, sha256 a612d67283e61479…

48: PHASE HCP_A3 %A 2 1 0.5 !
49: CONST HCP_A3 : NI : VA : !

NiO-95Kow.tdb: HCP_A3, type code %A, sha256 a7d68a7866eed0eb…

50: PHASE HCP_A3 %A 2 1 0.5 !
51: CONST HCP_A3 : NI : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

ION (Ni–O)

Id: phase:ni-o:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 1714.17–2500 K, x(O) 0–0.49912
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:ion
tdb: tdb:NiO-90Tay.tdb:ION, tdb:NiO-95Kow.tdb:ION

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

NiO-90Tay.tdb: ION, type code %, sha256 a612d67283e61479…

30: PHASE ION:Y % 2 1 1 !
31: CONST ION:Y : NI+2 : O-2 VA O : !

NiO-95Kow.tdb: ION, type code %, sha256 a7d68a7866eed0eb…

32: PHASE ION:Y % 2 1 1 !
33: CONST ION:Y : NI+2 : O-2 VA : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

LIQUID (Ni–O)

Id: phase:ni-o:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 1720–2500 K, x(O) 0–0.49
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:liquid
tdb: tdb:NiO-90Tay.tdb:LIQUID, tdb:NiO-95Kow.tdb:LIQUID

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

NiO-90Tay.tdb: LIQUID, type code %, sha256 a612d67283e61479…

33: PHASE LIQUID:L % 1 1 !
34: CONST LIQUID:L : NI : !

NiO-95Kow.tdb: LIQUID, type code %, sha256 a7d68a7866eed0eb…

35: PHASE LIQUID:L % 1 1 !
36: CONST LIQUID:L : NI NIO : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
assessment that models this phase

O2GAS (Ni–O)

Id: phase:ni-o:o2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–1620 K, x(O) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:ni-o:o2gas
tdb: tdb:NiO-90Tay.tdb:O2GAS, tdb:NiO-95Kow.tdb:O2GAS

TDB models of O2GAS (2): PHASE and CONSTITUENT statements as written

NiO-90Tay.tdb: O2GAS, type code %, sha256 a612d67283e61479…

59: PHASE O2GAS % 1 1 !
60: CONST O2GAS : O2 : !

NiO-95Kow.tdb: O2GAS, type code %, sha256 a7d68a7866eed0eb…

61: PHASE O2GAS % 1 1 !
62: CONST O2GAS : O2 : !

Example references (2 of 2; assessments first):

doi:10.1016/0364-5916(95)00024-9 M. Kowalski, P.J. Spencer, Calphad, 19, 229-43(1995).
assessment that models this phase
doi:10.1515/ijmr-1990-810509 J.R. Taylor, A.T. Dinsdale, Z. Metallkd., 81, 354-66(1990).
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}
}