O–Th phases

6 phases (tier A 3, liquid 2, gas 1); 5 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 · O–Th system page · Markdown · field reference

Phases of the O–Th system (6)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
BCC_A2 phase:o-th:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 1633.2–2022.99 K, x(O) 0–0	0	2
FCC_A1 phase:o-th:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1633.2 K, x(O) 0–0	0	2
ION phase:o-th:ion	liquid	liquid	stable in 2 of 2 calculated diagram(s): 2006.45–4000 K, x(O) 0–0.67229	0	2
LIQUID phase:o-th:liquid	liquid	liquid	not stable in 2 calculated diagram(s)	6	2
O2GAS phase:o-th:o2gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–4000 K, x(O) 1–1	0	2
THO2_C1 phase:o-th:tho2-c1	CaF2 · C1 · cF12 · Fm-3m (225)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–3680.2 K, x(O) 0.65904–0.66667	0	2

BCC_A2 (O–Th)

Id: phase:o-th:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stoichiometry: Th 1.0000
Stability: stable in 2 of 2 calculated diagram(s): 1633.2–2022.99 K, x(O) 0–0
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-th:bcc-a2
tdb: tdb:ThO-03Kin.tdb:BCC_A2, tdb:ThO-18Ber.tdb:BCC_A2

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

ThO-03Kin.tdb: BCC_A2, type code %B, sha256 640414db2a764520…

42: PHASE BCC_A2 %B 2 1 3 !
43: CONST BCC_A2 : TH : VA : !

ThO-18Ber.tdb: BCC_A2, type code %B, sha256 7787fa4553bd2bc8…

47: PHASE BCC_A2 %B 2 1 3 !
48: CONST BCC_A2 : TH : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
assessment that models this phase

FCC_A1 (O–Th)

Id: phase:o-th:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stoichiometry: Th 1.0000
Stability: stable in 2 of 2 calculated diagram(s): 300–1633.2 K, x(O) 0–0
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-th:fcc-a1
tdb: tdb:ThO-03Kin.tdb:FCC_A1, tdb:ThO-18Ber.tdb:FCC_A1

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

ThO-03Kin.tdb: FCC_A1, type code %, sha256 640414db2a764520…

37: PHASE FCC_A1 % 2 1 1 !
38: CONST FCC_A1 : TH : VA : !

ThO-18Ber.tdb: FCC_A1, type code %, sha256 7787fa4553bd2bc8…

42: PHASE FCC_A1 % 2 1 1 !
43: CONST FCC_A1 : TH : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
assessment that models this phase

ION (O–Th)

Id: phase:o-th:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 2006.45–4000 K, x(O) 0–0.67229
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-th:ion
tdb: tdb:ThO-03Kin.tdb:ION, tdb:ThO-18Ber.tdb:ION

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

ThO-03Kin.tdb: ION, type code %, sha256 640414db2a764520…

29: PHASE ION:Y % 2 1 1 !
30: CONST ION:Y : TH+4 : O-2 VA O : !

ThO-18Ber.tdb: ION, type code %, sha256 7787fa4553bd2bc8…

34: PHASE ION:Y % 2 1 1 !
35: CONST ION:Y : TH+4 : O-2 VA O : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
assessment that models this phase

LIQUID (O–Th)

Id: phase:o-th:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stoichiometry: Th 1.0000
Stability: not stable in 2 calculated diagram(s)
Literature: 6 values (6 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:o-th:liquid
paper: paper:10.1016/j.jnucmat.2018.09.013:liquid
tdb: tdb:ThO-03Kin.tdb:LIQUID, tdb:ThO-18Ber.tdb:LIQUID

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

ThO-03Kin.tdb: LIQUID, type code %, sha256 640414db2a764520…

32: PHASE LIQUID:L % 1 1 !
33: CONST LIQUID:L : TH : !

ThO-18Ber.tdb: LIQUID, type code %, sha256 7787fa4553bd2bc8…

37: PHASE LIQUID:L % 1 1 !
38: CONST LIQUID:L : TH : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase; reports values for this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
assessment that models this phase

O2GAS (O–Th)

Id: phase:o-th:o2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–4000 K, x(O) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-th:o2gas
tdb: tdb:ThO-03Kin.tdb:O2GAS, tdb:ThO-18Ber.tdb:O2GAS

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

ThO-03Kin.tdb: O2GAS, type code %, sha256 640414db2a764520…

50: PHASE O2GAS % 1 1 !
51: CONST O2GAS : O2 :!

ThO-18Ber.tdb: O2GAS, type code %, sha256 7787fa4553bd2bc8…

55: PHASE O2GAS % 1 1 !
56: CONST O2GAS : O2 :!

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
assessment that models this phase

THO2_C1 (O–Th)

Id: phase:o-th:tho2-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 2 of 2 calculated diagram(s): 300–3680.2 K, x(O) 0.65904–0.66667
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-th:tho2-c1
tdb: tdb:ThO-03Kin.tdb:THO2_C1, tdb:ThO-18Ber.tdb:THO2_C1

TDB models of THO2_C1 (2): PHASE and CONSTITUENT statements as written

ThO-03Kin.tdb: THO2_C1, type code %, sha256 640414db2a764520…

47: PHASE THO2_C1 % 2 1 2 !
48: CONST THO2_C1 : TH : O% VA : !

ThO-18Ber.tdb: THO2_C1, type code %, sha256 7787fa4553bd2bc8…

52: PHASE THO2_C1:I % 3 1 2 1 !
53: CONST THO2_C1:I : TH+3 TH+4% : O-2% VA : O-2 VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2018.09.013 A. Bergeron, D. Manara, O. Beneš, R. Eloirdi, M.H.A. Piro, E.C. Corcoran, Thermodynamic modelling of thoria-urania and thoria-plutonia fuels: Description of the Th-U-Pu-O quaternary system, Journal of Nuclear Materials 512, 324-348 (2018).
assessment that models this phase
doi:10.1016/S0021-9614(03)00002-8 H. Kinoshita, D. Setoyama, Y. Saito, M. Hirota, K. Kurosaki, M. Uno, S. Yamanaka, J. Chem. Thermodyn., 35, 719-31(2003).
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}
}