# O–Th phases > O–Th system: 6 phases (tier A 3, liquid 2, gas 1); 5 stable in a calculated diagram in the ORCHID phase registry, with names, structure type when the stored evidence supports an assignment under the stated tier rules, calculated stability, verbatim TDB PHASE/CONSTITUENT statements and example references. HTML: https://data.orchid-project.org/phases/pages/O-TH.html · Markdown: https://data.orchid-project.org/phases/pages/O-TH.md 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](https://orchid-project.org/phases/?q=O-TH) · [full JSON](https://data.orchid-project.org/phases/systems/O-TH.json) · [O–Th system page](https://data.orchid-project.org/systems/O-TH.html) · [Markdown](https://data.orchid-project.org/phases/pages/O-TH.md) · [field reference](https://data.orchid-project.org/phases/SCHEMA.md) Table: Phases of the O–Th system (6) | Phase | Structure | Basis | Stability (calculated) | Literature values | TDB models | |---|---|---|---|---:|---:| | [BCC_A2](#phase-o-th-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); _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); _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); _phase:o-th:liquid_ | liquid | liquid | not stable in 2 calculated diagram(s) | 6 | 2 | | [O2GAS](#phase-o-th-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); _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](https://orchid-project.org/phases/#phase:o-th:bcc-a2) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): BCC_A2, type code %B, sha256 `640414db2a764520…` ~~~~text 42: PHASE BCC_A2 %B 2 1 3 ! 43: CONST BCC_A2 : TH : VA : ! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): BCC_A2, type code %B, sha256 `7787fa4553bd2bc8…` ~~~~text 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](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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](https://orchid-project.org/phases/#phase:o-th:fcc-a1) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): FCC_A1, type code %, sha256 `640414db2a764520…` ~~~~text 37: PHASE FCC_A1 % 2 1 1 ! 38: CONST FCC_A1 : TH : VA : ! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): FCC_A1, type code %, sha256 `7787fa4553bd2bc8…` ~~~~text 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](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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](https://orchid-project.org/phases/#phase:o-th:ion) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): ION, type code %, sha256 `640414db2a764520…` ~~~~text 29: PHASE ION:Y % 2 1 1 ! 30: CONST ION:Y : TH+4 : O-2 VA O : ! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): ION, type code %, sha256 `7787fa4553bd2bc8…` ~~~~text 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](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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](https://orchid-project.org/phases/#phase:o-th:liquid) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): LIQUID, type code %, sha256 `640414db2a764520…` ~~~~text 32: PHASE LIQUID:L % 1 1 ! 33: CONST LIQUID:L : TH : ! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): LIQUID, type code %, sha256 `7787fa4553bd2bc8…` ~~~~text 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](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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](https://orchid-project.org/phases/#phase:o-th:o2gas) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): O2GAS, type code %, sha256 `640414db2a764520…` ~~~~text 50: PHASE O2GAS % 1 1 ! 51: CONST O2GAS : O2 :! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): O2GAS, type code %, sha256 `7787fa4553bd2bc8…` ~~~~text 55: PHASE O2GAS % 1 1 ! 56: CONST O2GAS : O2 :! ~~~~ Example references (2 of 2; assessments first): - [doi:10.1016/j.jnucmat.2018.09.013](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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](https://orchid-project.org/phases/#phase:o-th:tho2-c1) 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](https://orchid-project.org/data/databases/sgte-binary/ThO-03Kin.tdb): THO2_C1, type code %, sha256 `640414db2a764520…` ~~~~text 47: PHASE THO2_C1 % 2 1 2 ! 48: CONST THO2_C1 : TH : O% VA : ! ~~~~ [ThO-18Ber.tdb](https://orchid-project.org/data/databases/sgte-binary/ThO-18Ber.tdb): THO2_C1, type code %, sha256 `7787fa4553bd2bc8…` ~~~~text 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](https://doi.org/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](https://doi.org/10.1016/S0021-9614%2803%2900002-8) 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). https://doi.org/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). https://doi.org/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. ```bibtex @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} } ``` --- Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite the ORCHID phase registry and the sources named on the page (TDB assessments, Hallstedt 2025, Materials Project, OQMD). TDB statements are quoted as written; parameter expressions are not reproduced. Field reference: [SCHEMA.md](https://data.orchid-project.org/phases/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt).