Bi–U phases

10 phases (tier A 7, tier C 1, liquid 1, needs_review 1); 8 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 · Bi–U system page · Markdown · field reference

Phases of the Bi–U system (10)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
ORTHORHOMBIC_A20 phase:bi-u:a20-orthorhombic	alpha-U · A20 · oC4 · Cmcm (63)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–942.03 K, x(U) 1–1	0	2
RHOMBOHEDRAL_A7 phase:bi-u:a7-rhombohedral	alpha-As · A7 · hR2 · R-3m (166)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–544.55 K, x(U) 0–0	2	2
BCC_A2 phase:bi-u:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 1048.99–3999.24 K, x(U) 0.99998–1	4	2
BI2U phase:bi-u:bi2u	UAs2 · tP6 · P4/nmm (129)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 2 of 2 calculated diagram(s): 300–1281.52 K, x(U) 0.33333–0.33333	76	2
BI4U3_D73 phase:bi-u:bi4u3-d73	Th3P4 · D7_3 · cI28 · I-43d (220)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1424.47 K, x(U) 0.42857–0.42857	4	2
BIU_B1 phase:bi-u:biu-b1	NaCl · B1 · cF8 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1674.42 K, x(U) 0.5–0.5	10	2
FCC_A1 phase:bi-u:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 2 calculated diagram(s)	0	2
HCP_A3 phase:bi-u:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	0	2
LIQUID phase:bi-u:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 542.38–4000 K, x(U) 0–1	11	2
TETRAGONAL_U phase:bi-u:u-tetragonal		needs_review	stable in 2 of 2 calculated diagram(s): 300.78–1403.99 K, x(U) 1–1	0	2

ORTHORHOMBIC_A20 (Bi–U)

Id: phase:bi-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 2 of 2 calculated diagram(s): 300–942.03 K, x(U) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:bi-u:a20-orthorhombic, corpus:phase:bi-u:orthorhombic-a20
tdb: tdb:BiU-11Wan.tdb:ORTHORHOMBIC_A20, tdb:BiU-21Aga.tdb:ORTHORHOMBIC_A20

TDB models of ORTHORHOMBIC_A20 (2): PHASE and CONSTITUENT statements as written

BiU-11Wan.tdb: ORTHORHOMBIC_A20, type code %, sha256 7dd97a31494481fb…

47: PHASE ORTHORHOMBIC_A20 % 1 1 !
48: CONST ORTHORHOMBIC_A20 : U : !

BiU-21Aga.tdb: ORTHORHOMBIC_A20, type code %, sha256 54437879543405d4…

52: PHASE ORTHORHOMBIC_A20 % 1 1 !
53: CONST ORTHORHOMBIC_A20 : BI U% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

RHOMBOHEDRAL_A7 (Bi–U)

Id: phase:bi-u: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
Stability: stable in 2 of 2 calculated diagram(s): 300–544.55 K, x(U) 0–0
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:bi-u:a7-rhombohedral, corpus:phase:bi-u:rhombohedral-a7
paper: paper:10.1016/j.jnucmat.2011.02.021:Bi
tdb: tdb:BiU-11Wan.tdb:RHOMBOHEDRAL_A7, tdb:BiU-21Aga.tdb:RHOMBOHEDRAL_A7

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

BiU-11Wan.tdb: RHOMBOHEDRAL_A7, type code %, sha256 7dd97a31494481fb…

42: PHASE RHOMBOHEDRAL_A7 % 1 1 !
43: CONST RHOMBOHEDRAL_A7 : BI : !

BiU-21Aga.tdb: RHOMBOHEDRAL_A7, type code %, sha256 54437879543405d4…

47: PHASE RHOMBOHEDRAL_A7 % 1 1 !
48: CONST RHOMBOHEDRAL_A7 : BI% U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

BCC_A2 (Bi–U)

Id: phase:bi-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 2 of 2 calculated diagram(s): 1048.99–3999.24 K, x(U) 0.99998–1
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:bi-u:bcc-a2
paper: paper:10.1016/j.jnucmat.2011.02.021:γU
tdb: tdb:BiU-11Wan.tdb:BCC_A2, tdb:BiU-21Aga.tdb:BCC_A2

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

BiU-11Wan.tdb: BCC_A2, type code %B, sha256 7dd97a31494481fb…

32: PHASE BCC_A2 %B 2 1 3 !
33: CONST BCC_A2 : BI U% : VA : !

BiU-21Aga.tdb: BCC_A2, type code %B, sha256 54437879543405d4…

37: PHASE BCC_A2 %B 2 1 3 !
38: CONST BCC_A2 : BI U% : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

BI2U (Bi–U)

Id: phase:bi-u:bi2u; status assigned
Structure: UAs2 · tP6 · P4/nmm (129); type st:uas2-tp6; 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_on_hull_entry_in_both, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
Stoichiometry: Bi 0.6667, U 0.3333
Stability: stable in 2 of 2 calculated diagram(s): 300–1281.52 K, x(U) 0.33333–0.33333
Literature: 76 values (76 accepted) from 2 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:bi-u:bi2u
paper: paper:10.1016/j.jnucmat.2011.02.021:UBi2, paper:10.1016/j.tca.2021.178913:Bi2U(s)
tdb: tdb:BiU-11Wan.tdb:BI2U, tdb:BiU-21Aga.tdb:BI2U

TDB models of BI2U (2): PHASE and CONSTITUENT statements as written

BiU-11Wan.tdb: BI2U, type code %, sha256 7dd97a31494481fb…

57: PHASE BI2U % 2 2 1 !
58: CONST BI2U : BI : U : !

BiU-21Aga.tdb: BI2U, type code %, sha256 54437879543405d4…

62: PHASE BI2U % 2 2 1 !
63: CONST BI2U : BI : U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase

BI4U3_D73 (Bi–U)

Id: phase:bi-u:bi4u3-d73; status assigned
Structure: Th3P4 · D7_3 · cI28 · I-43d (220); type st:d7-3-th3p4-ci28; tier A: standard phase name; confidence high
Stoichiometry: Bi 0.5714, U 0.4286
Stability: stable in 2 of 2 calculated diagram(s): 300–1424.47 K, x(U) 0.42857–0.42857
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:bi-u:bi4u3-d73
paper: paper:10.1016/j.jnucmat.2011.02.021:U3Bi4
tdb: tdb:BiU-11Wan.tdb:BI4U3_D73, tdb:BiU-21Aga.tdb:BI4U3_D73

TDB models of BI4U3_D73 (2): PHASE and CONSTITUENT statements as written

BiU-11Wan.tdb: BI4U3_D73, type code %, sha256 7dd97a31494481fb…

62: PHASE BI4U3_D73 % 2 4 3 !
63: CONST BI4U3_D73 : BI : U : !

BiU-21Aga.tdb: BI4U3_D73, type code %, sha256 54437879543405d4…

67: PHASE BI4U3_D73 % 2 4 3 !
68: CONST BI4U3_D73 : BI : U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

BIU_B1 (Bi–U)

Id: phase:bi-u:biu-b1; status assigned
Structure: NaCl · B1 · cF8 · Fm-3m (225); type st:b1-nacl-cf8; tier A: standard phase name; confidence high
Stoichiometry: Bi 0.5000, U 0.5000
Stability: stable in 2 of 2 calculated diagram(s): 300–1674.42 K, x(U) 0.5–0.5
Literature: 10 values (10 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:bi-u:biu-b1
paper: paper:10.1016/j.jnucmat.2011.02.021:UBi
tdb: tdb:BiU-11Wan.tdb:BIU_B1, tdb:BiU-21Aga.tdb:BIU_B1

TDB models of BIU_B1 (2): PHASE and CONSTITUENT statements as written

BiU-11Wan.tdb: BIU_B1, type code %, sha256 7dd97a31494481fb…

67: PHASE BIU_B1 % 2 1 1 !
68: CONST BIU_B1 : BI : U : !

BiU-21Aga.tdb: BIU_B1, type code %, sha256 54437879543405d4…

72: PHASE BIU_B1 % 2 1 1 !
73: CONST BIU_B1 : BI : U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

FCC_A1 (Bi–U)

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

Names (3): corpus: corpus:phase:bi-u:fcc-a1
tdb: tdb:BiU-11Wan.tdb:FCC_A1, tdb:BiU-21Aga.tdb:FCC_A1

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

BiU-11Wan.tdb: FCC_A1, type code %A, sha256 7dd97a31494481fb…

27: PHASE FCC_A1 %A 2 1 1 !
28: CONST FCC_A1 : BI U : VA : !

BiU-21Aga.tdb: FCC_A1, type code %A, sha256 54437879543405d4…

32: PHASE FCC_A1 %A 2 1 1 !
33: CONST FCC_A1 : BI U : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

HCP_A3 (Bi–U)

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

Names (3): corpus: corpus:phase:bi-u:hcp-a3
tdb: tdb:BiU-11Wan.tdb:HCP_A3, tdb:BiU-21Aga.tdb:HCP_A3

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

BiU-11Wan.tdb: HCP_A3, type code %A, sha256 7dd97a31494481fb…

37: PHASE HCP_A3 %A 2 1 0.5 !
38: CONST HCP_A3 : BI U : VA: !

BiU-21Aga.tdb: HCP_A3, type code %A, sha256 54437879543405d4…

42: PHASE HCP_A3 %A 2 1 0.5 !
43: CONST HCP_A3 : BI U : VA: !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

LIQUID (Bi–U)

Id: phase:bi-u:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 542.38–4000 K, x(U) 0–1
Literature: 11 values (11 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:bi-u:liquid
paper: paper:10.1016/j.jnucmat.2011.02.021:L, paper:10.1016/j.jnucmat.2011.02.021:L2
tdb: tdb:BiU-11Wan.tdb:LIQUID, tdb:BiU-21Aga.tdb:LIQUID

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

BiU-11Wan.tdb: LIQUID, type code %, sha256 7dd97a31494481fb…

22: PHASE LIQUID:L % 1 1 !
23: CONST LIQUID:L : BI U : !

BiU-21Aga.tdb: LIQUID, type code %, sha256 54437879543405d4…

27: PHASE LIQUID:L % 1 1 !
28: CONST LIQUID:L : BI U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
assessment that models this phase

TETRAGONAL_U (Bi–U)

Id: phase:bi-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 — BiU-11Wan.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — BiU-21Aga.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Stability: stable in 2 of 2 calculated diagram(s): 300.78–1403.99 K, x(U) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:bi-u:u-tetragonal, corpus:phase:bi-u:tetragonal-u
tdb: tdb:BiU-11Wan.tdb:TETRAGONAL_U, tdb:BiU-21Aga.tdb:TETRAGONAL_U

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

BiU-11Wan.tdb: TETRAGONAL_U, type code %, sha256 7dd97a31494481fb…

52: PHASE TETRAGONAL_U % 1 1 !
53: CONST TETRAGONAL_U : U : !

BiU-21Aga.tdb: TETRAGONAL_U, type code %, sha256 54437879543405d4…

57: PHASE TETRAGONAL_U % 1 1 !
58: CONST TETRAGONAL_U : BI U% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.02.021 C.P. Wang, W.J. Yu, Z.S. Li, X.J. Liu, A.T. Tang, F.S. Pan, Thermodynamic assessments of the Bi–U and Bi–Mn systems, Journal of Nuclear Materials 412, 66-71 (2011).
assessment that models this phase
doi:10.1016/j.tca.2021.178913 Renu Agarwal, Understanding uranium interactions with bismuth and lead-bismuth eutectic: Using calorimetric measurements, Thermochimica Acta 699, 178913 (2021).
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}
}