Co–U phases

12 phases (tier A 7, tier C 2, liquid 1, needs_review 2); 12 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 · Co–U system page · Markdown · field reference

Phases of the Co–U system (12)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
ORTHORHOMBIC_A20 phase:co-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) 1–1	0	1
BCC_A2 phase:co-u:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 1031.83–3998.8 K, x(U) 0.96579–1	4	1
CO11U2 phase:co-u:co11u2	Co5U · hR18 · R-3m (166)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 1 of 1 calculated diagram(s): 324.47–1398.96 K, x(U) 0.15385–0.15385	6	1
CO2U_C15 phase:co-u:co2u-c15	Cu2Mg · C15 · cF24 · Fd-3m (227)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–1454.51 K, x(U) 0.2944–0.3336	8	1
CO3U phase:co-u:co3u	Ni3Pu · hR12 · R-3m (166)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 1 of 1 calculated diagram(s): 300–1111.22 K, x(U) 0.25–0.25	2	1
CO4U phase:co-u:co4u		needs_review	stable in 1 of 1 calculated diagram(s): 300–1387.89 K, x(U) 0.2–0.2	8	1
COU_BA phase:co-u:cou-ba	CoU · B_a · cI16 · I2_13 (199)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–1075.63 K, x(U) 0.5–0.5	4	1
COU6_D2C phase:co-u:cou6-d2c	MnU6 · D2_c · tI28 · I4/mcm (140)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–1097.55 K, x(U) 0.85714–0.85714	4	1
FCC_A1 phase:co-u:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 694.99–1799.64 K, x(U) 0–5e-05	2	1
HCP_A3 phase:co-u:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	stable in 1 of 1 calculated diagram(s): 300–694.99 K, x(U) 0–0	0	1
LIQUID phase:co-u:liquid	liquid	liquid	stable in 1 of 1 calculated diagram(s): 1014.02–4000 K, x(U) 0–1	18	1
TETRAGONAL_U phase:co-u:u-tetragonal		needs_review	stable in 1 of 1 calculated diagram(s): 942.02–1406.83 K, x(U) 1–1	0	1

ORTHORHOMBIC_A20 (Co–U)

Id: phase:co-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
Stoichiometry: U 1.0000
Stability: stable in 1 of 1 calculated diagram(s): 300–942.02 K, x(U) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:a20-orthorhombic, corpus:phase:co-u:orthorhombic-a20
tdb: tdb:CoU-08Wan.tdb:ORTHORHOMBIC_A20

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

CoU-08Wan.tdb: ORTHORHOMBIC_A20, type code %, sha256 91f49d0dd36e4d3c…

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

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase

BCC_A2 (Co–U)

Id: phase:co-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): 1031.83–3998.8 K, x(U) 0.96579–1
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:co-u:bcc-a2
paper: paper:10.1016/j.jnucmat.2007.06.023:γ (U), paper:10.1016/j.jnucmat.2007.06.023:γ(U)
tdb: tdb:CoU-08Wan.tdb:BCC_A2

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

CoU-08Wan.tdb: BCC_A2, type code %B, sha256 91f49d0dd36e4d3c…

36: PHASE BCC_A2 %B 2 1 3 !
37: CONST BCC_A2 : CO U% : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

CO11U2 (Co–U)

Id: phase:co-u:co11u2; status assigned
Structure: Co5U · hR18 · R-3m (166); type st:co5u-hr18; 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: Co 0.8462, U 0.1538
Stability: stable in 1 of 1 calculated diagram(s): 324.47–1398.96 K, x(U) 0.15385–0.15385
Literature: 6 values (6 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:co11u2
paper: paper:10.1016/j.jnucmat.2007.06.023:Co11 U2
tdb: tdb:CoU-08Wan.tdb:CO11U2

TDB models of CO11U2 (1): PHASE and CONSTITUENT statements as written

CoU-08Wan.tdb: CO11U2, type code %, sha256 91f49d0dd36e4d3c…

56: PHASE CO11U2 % 2 11 2 !
57: CONST CO11U2 : CO : U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

CO2U_C15 (Co–U)

Id: phase:co-u:co2u-c15; status assigned
Structure: Cu2Mg · C15 · cF24 · Fd-3m (227); type st:c15-cu2mg-cf24; tier A: standard phase name; confidence high
Caveat: partitioned order/disorder model in CoU-08Wan.tdb also describes the disordered state
Stability: stable in 1 of 1 calculated diagram(s): 300–1454.51 K, x(U) 0.2944–0.3336
Literature: 8 values (8 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:co-u:co2u-c15
paper: paper:10.1016/j.jnucmat.2007.06.023:Co2 U, paper:10.1016/j.jnucmat.2007.06.023:Co2U
tdb: tdb:CoU-08Wan.tdb:CO2U_C15

TDB models of CO2U_C15 (1): PHASE and CONSTITUENT statements as written

CoU-08Wan.tdb: CO2U_C15, type code %, sha256 91f49d0dd36e4d3c…

71: PHASE CO2U_C15 % 2 2 1 !
72: CONST CO2U_C15 : CO% U : CO U% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

CO3U (Co–U)

Id: phase:co-u:co3u; status assigned
Structure: Ni3Pu · hR12 · R-3m (166); type st:ni3pu-hr12; 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_mp, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
Stoichiometry: Co 0.7500, U 0.2500
Stability: stable in 1 of 1 calculated diagram(s): 300–1111.22 K, x(U) 0.25–0.25
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:co3u
paper: paper:10.1016/j.jnucmat.2007.06.023:Co3U
tdb: tdb:CoU-08Wan.tdb:CO3U

TDB models of CO3U (1): PHASE and CONSTITUENT statements as written

CoU-08Wan.tdb: CO3U, type code %, sha256 91f49d0dd36e4d3c…

66: PHASE CO3U % 2 3 1 !
67: CONST CO3U : CO : U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

CO4U (Co–U)

Id: phase:co-u:co4u; status needs_review
No structure assigned. Why: no_on_hull_entry_in_both; no_structure_token; sgte_mmc2_row_incomplete
Candidate (literature_printed): (Co4U) · ? — printed with a label mapped to this phase
Candidate (sgte_mmc2): (Co4U) — Hallstedt 2025 mmc2 row for CO4U: Co4U
Stoichiometry: Co 0.8000, U 0.2000
Stability: stable in 1 of 1 calculated diagram(s): 300–1387.89 K, x(U) 0.2–0.2
Literature: 8 values (8 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:co4u
paper: paper:10.1016/j.jnucmat.2007.06.023:Co4U
tdb: tdb:CoU-08Wan.tdb:CO4U

TDB models of CO4U (1): PHASE and CONSTITUENT statements as written

CoU-08Wan.tdb: CO4U, type code %, sha256 91f49d0dd36e4d3c…

61: PHASE CO4U % 2 4 1 !
62: CONST CO4U : CO : U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

COU_BA (Co–U)

Id: phase:co-u:cou-ba; status assigned
Structure: CoU · B_a · cI16 · I2_13 (199); type st:b-a-cou-ci16; tier A: standard phase name; confidence high
Caveat: DFT agrees: on-hull mp-aaacjlup and oqmd-17123, space group 199
Stoichiometry: Co 0.5000, U 0.5000
Stability: stable in 1 of 1 calculated diagram(s): 300–1075.63 K, x(U) 0.5–0.5
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:co-u:cou-ba
mp: mp:mp-aaacjlup
oqmd: oqmd:oqmd-17123
paper: paper:10.1016/j.jnucmat.2007.06.023:CoU
tdb: tdb:CoU-08Wan.tdb:COU_BA

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

CoU-08Wan.tdb: COU_BA, type code %, sha256 91f49d0dd36e4d3c…

76: PHASE COU_BA % 2 1 1 !
77: CONST COU_BA : CO : U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

COU6_D2C (Co–U)

Id: phase:co-u:cou6-d2c; status assigned
Structure: MnU6 · D2_c · tI28 · I4/mcm (140); type st:d2-c-mnu6-ti28; tier A: standard phase name; confidence high
Stoichiometry: Co 0.1429, U 0.8571
Stability: stable in 1 of 1 calculated diagram(s): 300–1097.55 K, x(U) 0.85714–0.85714
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:co-u:cou6-d2c
paper: paper:10.1016/j.jnucmat.2007.06.023:CoU 6, paper:10.1016/j.jnucmat.2007.06.023:CoU6
tdb: tdb:CoU-08Wan.tdb:COU6_D2C

TDB models of COU6_D2C (1): PHASE and CONSTITUENT statements as written

CoU-08Wan.tdb: COU6_D2C, type code %, sha256 91f49d0dd36e4d3c…

81: PHASE COU6_D2C % 2 1 6 !
82: CONST COU6_D2C : CO : U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

FCC_A1 (Co–U)

Id: phase:co-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: stable in 1 of 1 calculated diagram(s): 694.99–1799.64 K, x(U) 0–5e-05
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:fcc-a1
paper: paper:10.1016/j.jnucmat.2007.06.023:fcc (Co)
tdb: tdb:CoU-08Wan.tdb:FCC_A1

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

CoU-08Wan.tdb: FCC_A1, type code %A, sha256 91f49d0dd36e4d3c…

31: PHASE FCC_A1 %A 2 1 1 !
32: CONST FCC_A1 : CO% U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

HCP_A3 (Co–U)

Id: phase:co-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: stable in 1 of 1 calculated diagram(s): 300–694.99 K, x(U) 0–0
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:co-u:hcp-a3
tdb: tdb:CoU-08Wan.tdb:HCP_A3

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

CoU-08Wan.tdb: HCP_A3, type code %A, sha256 91f49d0dd36e4d3c…

41: PHASE HCP_A3 %A 2 1 0.5 !
42: CONST HCP_A3 : CO% U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase

LIQUID (Co–U)

Id: phase:co-u:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 1014.02–4000 K, x(U) 0–1
Literature: 18 values (18 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:co-u:liquid
paper: paper:10.1016/j.jnucmat.2007.06.023:L
tdb: tdb:CoU-08Wan.tdb:LIQUID

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

CoU-08Wan.tdb: LIQUID, type code %, sha256 91f49d0dd36e4d3c…

26: PHASE LIQUID:L % 1 1 !
27: CONST LIQUID:L : CO U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (2008).
assessment that models this phase; reports values for this phase

TETRAGONAL_U (Co–U)

Id: phase:co-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 — CoU-08Wan.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Stoichiometry: U 1.0000
Stability: stable in 1 of 1 calculated diagram(s): 942.02–1406.83 K, x(U) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:co-u:u-tetragonal
tdb: tdb:CoU-08Wan.tdb:TETRAGONAL_U

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

CoU-08Wan.tdb: TETRAGONAL_U, type code %, sha256 91f49d0dd36e4d3c…

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

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2007.06.023 J. Wang, X.J. Liu, C.P. Wang, Thermodynamic modeling of the Al–U and Co–U systems, Journal of Nuclear Materials 374, 79-86 (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}
}