# O–Pr system > O–Pr system: 13 accepted literature values (phase transition 8, crystal structure 3, formation 1, heat capacity / entropy / enthalpy 1) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote. HTML: https://data.orchid-project.org/systems/O-PR.html · Markdown: https://data.orchid-project.org/systems/O-PR.md 13 accepted literature values from 1 paper(s) (experimental 6, model 7); 0 calculated phase diagram(s). Data: [JSON](https://data.orchid-project.org/literature/systems/O-PR.json) · [CSV](https://data.orchid-project.org/systems/O-PR.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#O-PR) · [phases (15)](https://data.orchid-project.org/phases/pages/O-PR.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/O-PR.html) · [Markdown](https://data.orchid-project.org/systems/O-PR.md) Table: Accepted values by evidence class | Evidence class | Values | |---|---:| | experimental | 6 | | model | 7 | Table: Accepted values by property group | Property group | Values | |---|---:| | phase transition | 8 | | formation | 1 | | heat capacity / entropy / enthalpy | 1 | | crystal structure | 3 | Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/O/O-PR.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/O/O-PR.json) · [CALPHAD hull PrO-16McM](https://data.orchid-project.org/hulls/calphad-sgte/O/O-PR--PrO-16McM.json) ## Formation enthalpies Literature values in kJ/mol-atom where the per-atom basis is known. DFT columns: the lowest-energy entry at the same composition (Materials Project 2026.04.13, OQMD v1.8; different energy references, never averaged), from [dft_parity.json](https://data.orchid-project.org/literature/dft_parity.json). Table: Enthalpies of formation, O–Pr system (1) | Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote | |---|---|---:|---:|---|---:|---:|---|---|---| | A-Pr2O3 | [Pr2O3](https://data.orchid-project.org/compounds/Pr2O3.html) | -361.98 kJ/mol-atom | 298.15 | model | -360.381 (mp-aaaaaysn) | -345.037 (oqmd-16545) | [1] ZINKEVICH 2007 | Table 6.1, p. 24, row 25; `ORC-64WTPTGMMD.52446f` | | ## Other properties ### Phase transition (8) Table: Phase transition, O–Pr system | Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote | |---|---:|---:|---|---|---|---|---| | Phase transition | 2223 K | 2223 | polymorphic: A ⟺ H; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Foex 1966_ | Table 2.1, p. 6, row 25; `ORC-QOWBUPNSXG` | | | Phase transition | 2303 K | 2303 | polymorphic: A ⟺ H; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Shevtchenko 1985_ | Table 2.1, p. 6, row 29; `ORC-LJ7VPSJYUJ` | | | Phase transition | 2318 K | 2318 | polymorphic: A ⟺ H; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Tresvyatkii 1971_ | Table 2.1, p. 6, row 27; `ORC-FZ74PK2EYW` | | | Phase transition | 2353 K | 2353 | polymorphic: A \<=> H; _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 2.2, p. 8, row 12; `ORC-G4OR7YPNNZ` | | | Phase transition | 2393 K | 2393 | polymorphic: H ⟺ X; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Tresvyatkii 1971_ | Table 2.1, p. 6, row 28; `ORC-DY7R27IDZT` | | | Phase transition | 2403 K | 2403 | polymorphic: H ⟺ X; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Shevtchenko 1985_ | Table 2.1, p. 6, row 30; `ORC-LPRLEEKM6X` | | | Phase transition | 2423 K | 2423 | polymorphic: H ⟺ X; _alloy: O 0.6, Pr 0.4_ | experimental | [1] ZINKEVICH 2007; _cites Foex 1966_ | Table 2.1, p. 6, row 26; `ORC-A3RB2EQR5A` | | | Phase transition | 2443 K | 2443 | polymorphic: H \<=> X; _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 2.2, p. 8, row 26; `ORC-25VIGXKQZ2` | | ### Heat capacity / entropy / enthalpy (1) Table: Heat capacity / entropy / enthalpy, O–Pr system | Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote | |---|---:|---:|---|---|---|---|---| | Entropy; _printed: °S_ | 152.74 unknown | 298.15 | A-Pr2O3; _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 6.1, p. 24, row 25; `ORC-64WTPTGMMD.6348a5` | | ### Crystal structure (3) Table: Crystal structure, O–Pr system | Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote | |---|---:|---:|---|---|---|---|---| | lattice molar volume | 46.675 cm3 mol-1 | 298.15 | Pr2O3 (A-type); _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 3.1, p. 12, row 5; `ORC-7BPDP7IZEV.08a4e5` | | | lattice molar volume | 47.545 cm3 mol-1 | 298.15 | Pr2O3 (B-type); _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 3.1, p. 12, row 5; `ORC-7BPDP7IZEV.1af1f6` | | | lattice molar volume | 52.202 cm3 mol-1 | 298.15 | Pr2O3 (C-type); _alloy: O 0.6, Pr 0.4_ | model | [1] ZINKEVICH 2007 | Table 3.1, p. 12, row 5; `ORC-7BPDP7IZEV.e1c894` | | ## Sources Reporting papers the values were read from (a value cited from another work names that work in its row). 1. M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007). [doi:10.1016/j.pmatsci.2006.09.002](https://doi.org/10.1016/j.pmatsci.2006.09.002) ## Please cite - R. Arróyave, J. Saal, D. Shin, ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/10.5281/zenodo.23735569 - R. Arróyave, J. Saal, D. Shin, ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD) (version 2026.10), Zenodo (2026). https://doi.org/10.5281/zenodo.23735891 - 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 the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work); 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); 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. 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_literature_2026, author = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon}, title = {{ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature}}, version = {2026.10}, publisher = {Zenodo}, year = {2026}, doi = {10.5281/zenodo.23735569}, url = {https://doi.org/10.5281/zenodo.23735569}, note = {Version 1, machine-extracted} } @misc{orchid_hulls_2026, author = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon}, title = {{ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD)}}, version = {2026.10}, publisher = {Zenodo}, year = {2026}, doi = {10.5281/zenodo.23735891}, url = {https://doi.org/10.5281/zenodo.23735891} } @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 ORCHID ([CITATION.cff](https://data.orchid-project.org/CITATION.cff)) and the original sources. Quotes are short excerpts kept so that each value can be checked; they remain under the publishers' copyright and are not relicensed. Source papers, page images and full text are not redistributed. Field reference: [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt). Found an error? The report link of a value (Markdown: its id, ORC-..., in the Location column) opens a pre-filled GitHub issue, https://github.com/orchid-calphad/orchid-data/issues/new?template=report-value-error.yml&record_id=\, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).