Nb–U phases

6 phases (tier A 4, liquid 1, needs_review 1); 4 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 · Nb–U system page · Markdown · field reference

Phases of the Nb–U system (6)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
ORTHORHOMBIC_A20 phase:nb-u:a20-orthorhombic	alpha-U · A20 · oC4 · Cmcm (63)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–942.02 K, x(U) 0.98625–1	4	1
BCC_A2 phase:nb-u:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–2971.74 K, x(U) 0–1	6	1
FCC_A1 phase:nb-u:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 1 calculated diagram(s)	0	1
HCP_A3 phase:nb-u:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 1 calculated diagram(s)	0	1
LIQUID phase:nb-u:liquid	liquid	liquid	stable in 1 of 1 calculated diagram(s): 300.49–4000 K, x(U) 0–1	0	1
TETRAGONAL_U phase:nb-u:u-tetragonal		needs_review	stable in 1 of 1 calculated diagram(s): 937.63–1402.63 K, x(U) 0.9872–1	2	1

ORTHORHOMBIC_A20 (Nb–U)

Id: phase:nb-u:a20-orthorhombic; status assigned
Structure: alpha-U · A20 · oC4 · Cmcm (63); type st:a20-alpha-u-oc4; tier A: standard phase name; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 300–942.02 K, x(U) 0.98625–1
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:nb-u:a20-orthorhombic, corpus:phase:nb-u:orthorhombic-a20
paper: paper:10.1016/j.jnucmat.2008.07.008:αU
tdb: tdb:NbU-08Liu.tdb:ORTHORHOMBIC_A20

TDB models of ORTHORHOMBIC_A20 (1): PHASE and CONSTITUENT statements as written

NbU-08Liu.tdb: ORTHORHOMBIC_A20, type code %, sha256 5357c3b05f77c858…

43: PHASE ORTHORHOMBIC_A20 % 1 1 !
44: CONST ORTHORHOMBIC_A20 : NB U% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase; reports values for this phase

BCC_A2 (Nb–U)

Id: phase:nb-u: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): 300–2971.74 K, x(U) 0–1
Literature: 6 values (6 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:nb-u:bcc-a2
paper: paper:10.1016/j.jnucmat.2008.07.008:(Nb), paper:10.1016/j.jnucmat.2008.07.008:(γU, Nb), paper:10.1016/j.jnucmat.2008.07.008:γU
tdb: tdb:NbU-08Liu.tdb:BCC_A2

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

NbU-08Liu.tdb: BCC_A2, type code %B, sha256 5357c3b05f77c858…

33: PHASE BCC_A2 %B 2 1 1.5 !
34: CONST BCC_A2 : NB% U% : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase; reports values for this phase

FCC_A1 (Nb–U)

Id: phase:nb-u: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 1 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:nb-u:fcc-a1
tdb: tdb:NbU-08Liu.tdb:FCC_A1

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

NbU-08Liu.tdb: FCC_A1, type code %A, sha256 5357c3b05f77c858…

28: PHASE FCC_A1 %A 2 1 1 !
29: CONST FCC_A1 : NB U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase

HCP_A3 (Nb–U)

Id: phase:nb-u: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:nb-u:hcp-a3
tdb: tdb:NbU-08Liu.tdb:HCP_A3

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

NbU-08Liu.tdb: HCP_A3, type code %, sha256 5357c3b05f77c858…

38: PHASE HCP_A3 % 2 1 0.5 !
39: CONST HCP_A3 : NB U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase

LIQUID (Nb–U)

Id: phase:nb-u:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 300.49–4000 K, x(U) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:nb-u:liquid
tdb: tdb:NbU-08Liu.tdb:LIQUID

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

NbU-08Liu.tdb: LIQUID, type code %, sha256 5357c3b05f77c858…

23: PHASE LIQUID:L % 1 1 !
24: CONST LIQUID:L : NB U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase

TETRAGONAL_U (Nb–U)

Id: phase:nb-u:u-tetragonal; status needs_review
No structure assigned. Why: name_has_descriptive_tokens:TETRAGONAL; no_structure_token
Candidate (sgte_mmc2): beta-U · A_b · tP30 · P4_2/mnm (136) — Hallstedt 2025 mmc2 row for TETRAGONAL_U: beta-U
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — NbU-08Liu.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Stability: stable in 1 of 1 calculated diagram(s): 937.63–1402.63 K, x(U) 0.9872–1
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:nb-u:u-tetragonal, corpus:phase:nb-u:tetragonal-u
paper: paper:10.1016/j.jnucmat.2008.07.008:βU
tdb: tdb:NbU-08Liu.tdb:TETRAGONAL_U

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

NbU-08Liu.tdb: TETRAGONAL_U, type code %, sha256 5357c3b05f77c858…

48: PHASE TETRAGONAL_U % 1 1 !
49: CONST TETRAGONAL_U : NB U% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2008.07.008 X.J. Liu, Z.S. Li, J. Wang, C.P. Wang, Thermodynamic modeling of the U–Mn and U–Nb systems, Journal of Nuclear Materials 380, 99-104 (2008).
assessment that models this phase; reports values for 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}
}