H–Nb phases

8 phases (tier A 4, tier C 1, liquid 1, 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 · H–Nb system page · Markdown · field reference

Phases of the H–Nb system (8)
Phase	Structure	Basis	Stability (calculated)	TDB models
BCC_A2 phase:h-nb:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–2750 K, x(H) 0–0.5104	2
FCC_A1 phase:h-nb:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
GAS phase:h-nb:gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–4000 K, x(H) 0.98989–1	2
H2GAS phase:h-nb:h2gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–1220 K, x(H) 1–1	2
HCP_A3 phase:h-nb:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
LIQUID phase:h-nb:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 2748.56–4000 K, x(H) 0–0.00504	2
NBH phase:h-nb:nbh	NbH · oP8 · Pnnn (48)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 2 of 2 calculated diagram(s): 300–429.33 K, x(H) 0.40775–0.5	2
NBH2_C1 phase:h-nb:nbh2-c1	CaF2 · C1 · cF12 · Fm-3m (225)	tier A: standard phase name	stable in 1 of 2 calculated diagram(s): 300–430.66 K, x(H) 0.66285–0.66662	2

BCC_A2 (H–Nb)

Id: phase:h-nb: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): 300–2750 K, x(H) 0–0.5104
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:bcc-a2
tdb: tdb:NbH-23Dot.tdb:BCC_A2, tdb:NbH-97Ans-LB.tdb:BCC_A2

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

NbH-23Dot.tdb: BCC_A2, type code %B, sha256 79b1cf5db71443aa…

35: PHASE BCC_A2 %B 2 1 3 !
36: CONST BCC_A2 : NB% : H VA% : !

NbH-97Ans-LB.tdb: BCC_A2, type code %B, sha256 5f71226cd001bd44…

34: PHASE BCC_A2 %B 2 1 3 !
35: CONST BCC_A2 : NB% : H VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

FCC_A1 (H–Nb)

Id: phase:h-nb:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; 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:h-nb:fcc-a1
tdb: tdb:NbH-23Dot.tdb:FCC_A1, tdb:NbH-97Ans-LB.tdb:FCC_A1

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

NbH-23Dot.tdb: FCC_A1, type code %A, sha256 79b1cf5db71443aa…

30: PHASE FCC_A1 %A 2 1 1 !
31: CONST FCC_A1 : NB : H VA% : !

NbH-97Ans-LB.tdb: FCC_A1, type code %A, sha256 5f71226cd001bd44…

29: PHASE FCC_A1 %A 2 1 1 !
30: CONST FCC_A1 : NB : H VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

GAS (H–Nb)

Id: phase:h-nb:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–4000 K, x(H) 0.98989–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:gas
tdb: tdb:NbH-23Dot.tdb:GAS, tdb:NbH-97Ans-LB.tdb:GAS

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

NbH-23Dot.tdb: GAS, type code %, sha256 79b1cf5db71443aa…

54: PHASE GAS:G % 1 1 !
55: CONST GAS:G : NB H H2 : !

NbH-97Ans-LB.tdb: GAS, type code %, sha256 5f71226cd001bd44…

53: PHASE GAS:G % 1 1 !
54: CONST GAS:G : H H2 : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

H2GAS (H–Nb)

Id: phase:h-nb:h2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–1220 K, x(H) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:h2gas
tdb: tdb:NbH-23Dot.tdb:H2GAS, tdb:NbH-97Ans-LB.tdb:H2GAS

TDB models of H2GAS (2): PHASE and CONSTITUENT statements as written

NbH-23Dot.tdb: H2GAS, type code %, sha256 79b1cf5db71443aa…

57: PHASE H2GAS % 1 1 !
58: CONST H2GAS : H2 : !

NbH-97Ans-LB.tdb: H2GAS, type code %, sha256 5f71226cd001bd44…

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

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

HCP_A3 (H–Nb)

Id: phase:h-nb: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:h-nb:hcp-a3
tdb: tdb:NbH-23Dot.tdb:HCP_A3, tdb:NbH-97Ans-LB.tdb:HCP_A3

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

NbH-23Dot.tdb: HCP_A3, type code %A, sha256 79b1cf5db71443aa…

40: PHASE HCP_A3 %A 2 1 2 !
41: CONST HCP_A3 : NB : H VA% : !

NbH-97Ans-LB.tdb: HCP_A3, type code %A, sha256 5f71226cd001bd44…

39: PHASE HCP_A3 %A 2 1 0.5 !
40: CONST HCP_A3 : NB : H VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

LIQUID (H–Nb)

Id: phase:h-nb:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 2748.56–4000 K, x(H) 0–0.00504
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:liquid
tdb: tdb:NbH-23Dot.tdb:LIQUID, tdb:NbH-97Ans-LB.tdb:LIQUID

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

NbH-23Dot.tdb: LIQUID, type code %, sha256 79b1cf5db71443aa…

25: PHASE LIQUID:L % 1 1 !
26: CONST LIQUID:L : H NB : !

NbH-97Ans-LB.tdb: LIQUID, type code %, sha256 5f71226cd001bd44…

24: PHASE LIQUID:L % 1 1 !
25: CONST LIQUID:L : H NB : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

NBH (H–Nb)

Id: phase:h-nb:nbh; status assigned
Structure: NbH · oP8 · Pnnn (48); type st:nbh-op8; 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
Caveat: not certain from the name or DFT alone (no_structure_token, off_stoichiometric_model); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: stable in 2 of 2 calculated diagram(s): 300–429.33 K, x(H) 0.40775–0.5
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:nbh
tdb: tdb:NbH-23Dot.tdb:NBH, tdb:NbH-97Ans-LB.tdb:NBH

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

NbH-23Dot.tdb: NBH, type code %, sha256 79b1cf5db71443aa…

46: PHASE NBH % 2 1 1 !
47: CONST NBH : NB : H% VA : !

NbH-97Ans-LB.tdb: NBH, type code %, sha256 5f71226cd001bd44…

45: PHASE NBH % 2 1 1 !
46: CONST NBH : NB : H% VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
assessment that models this phase

NBH2_C1 (H–Nb)

Id: phase:h-nb:nbh2-c1; status assigned
Structure: CaF2 · C1 · cF12 · Fm-3m (225); type st:c1-caf2-cf12; tier A: standard phase name; confidence high
Stability: stable in 1 of 2 calculated diagram(s): 300–430.66 K, x(H) 0.66285–0.66662
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-nb:nbh2-c1
tdb: tdb:NbH-23Dot.tdb:NBH2_C1, tdb:NbH-97Ans-LB.tdb:NBH2_C1

TDB models of NBH2_C1 (2): PHASE and CONSTITUENT statements as written

NbH-23Dot.tdb: NBH2_C1, type code %, sha256 79b1cf5db71443aa…

51: PHASE NBH2_C1 % 2 1 2 !
52: CONST NBH2_C1 : NB : H% VA : !

NbH-97Ans-LB.tdb: NBH2_C1, type code %, sha256 5f71226cd001bd44…

50: PHASE NBH2_C1 % 2 1 2 !
51: CONST NBH2_C1 : NB : H% VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2023.102617 Maxime Dottor, Jean-Claude Crivello, Jean-Marc Joubert, Critical reassessment of the H–Nb system and experimental investigation and thermodynamic modeling of the H–Nb–Zr system, Calphad 83, 102617 (2023).
assessment that models this phase
doi:10.1016/S0925-8388(96)02652-7 I. Ansara, N. Dupin, unpublished, 1997.
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}
}