# O–Pu system

> O–Pu system: 89 accepted literature values (invariant reaction 42, heat capacity / entropy / enthalpy 22, formation 18, crystal structure 5) 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-PU.html · Markdown: https://data.orchid-project.org/systems/O-PU.md

89 accepted literature values from 1 paper(s) (experimental 25, model 55, unspecified 9); 0 calculated phase diagram(s). 7 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: [JSON](https://data.orchid-project.org/literature/systems/O-PU.json) · [CSV](https://data.orchid-project.org/systems/O-PU.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#O-PU) · [phases (14)](https://data.orchid-project.org/phases/pages/O-PU.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/O-PU.html) · [Markdown](https://data.orchid-project.org/systems/O-PU.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 25 |
| model | 55 |
| unspecified | 9 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 42 |
| phase transition | 2 |
| formation | 18 |
| heat capacity / entropy / enthalpy | 22 |
| crystal structure | 5 |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/O/O-PU.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/O/O-PU.json) · [CALPHAD hull PuO-08Gue](https://data.orchid-project.org/hulls/calphad-sgte/O/O-PU--PuO-08Gue.json) · [CALPHAD hull PuO-11Gue](https://data.orchid-project.org/hulls/calphad-sgte/O/O-PU--PuO-11Gue.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the O–Pu system (42)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 4097 | congruent melting: L = G |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 1; `ORC-OPB2HS4QSC` |  |
| 3410 | congruent melting: L = G |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 2; `ORC-EEIZLSIDJF` |  |
| 2718 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333; L: O 0.666667, Pu 0.333333 | experimental | [1] Guéneau 2008; _cites Aitken 1968_ | Table 3, p. 9, row 15; `ORC-XILRIC33C3` |  |
| 2698 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333; L: O 0.666667, Pu 0.333333 | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 17; `ORC-7ZRCCV6XIG` |  |
| 2673 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333; L: O 0.666667, Pu 0.333333 | experimental | [1] Guéneau 2008; _cites Riley 1970_ | Table 3, p. 9, row 16; `ORC-DEZWH7MNAY` |  |
| 2673 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333; L: O 0.666667, Pu 0.333333 | experimental | [1] Guéneau 2008; _cites Russel 1961_ | Table 3, p. 9, row 13; `ORC-PI6B774447` |  |
| 2660 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333 (basis unresolved); L: O 0.666667, Pu 0.333333 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 18; `ORC-AHJS67KJ4L` |  |
| 2640 | L = G + PuO2-x | PuO2-x: O 0.666667, Pu 0.333333 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 3; `ORC-KNVTPJS44Z` |  |
| 2553 | congruent melting: PuO2 = L | PuO2: O 0.666667, Pu 0.333333; L: O 0.666667, Pu 0.333333 | experimental | [1] Guéneau 2008; _cites Chikalla 1964_ [doi](https://doi.org/10.1016/0022-3115%2864%2990132-1) | Table 3, p. 9, row 14; `ORC-3BJBG7NDWQ` |  |
| 2358 | congruent melting: Pu2O3 = L | Pu2O3: O 0.6, Pu 0.4; L: O 0.6, Pu 0.4 | experimental | [1] Guéneau 2008; _cites Chikalla 1964_ [doi](https://doi.org/10.1016/0022-3115%2864%2990132-1) | Table 3, p. 9, row 7; `ORC-ED5XOHJZLK` |  |
| 2353 | congruent melting: Pu2O3 = L | Pu2O3: O 0.6, Pu 0.4; L: O 0.6, Pu 0.4 | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 9; `ORC-KFY47Y4DSB` |  |
| 2348 | congruent melting: Pu2O3 = L | Pu2O3: O 0.6, Pu 0.4; L: O 0.6, Pu 0.4 | experimental | [1] Guéneau 2008; _cites Riley 1970_ | Table 3, p. 9, row 8; `ORC-PCXYKFL6B7` |  |
| 2330 | congruent melting: Pu2O3 = L | Pu2O3: O 0.6, Pu 0.4; L: O 0.6, Pu 0.4 | model | [1] Guéneau 2008 | Table 3, p. 9, row 10; `ORC-6TOK7Y3TVI` |  |
| 2306 | L = Pu2O3 + PuO2 | PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 12; `ORC-VZBBMVIEIU` |  |
| 2273 | L = Pu2O3 + PuO2 | PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 11; `ORC-OWNMVU4O6E` |  |
| 2122 | L2 = L1 + Pu2O3 |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 6; `ORC-NPPJNJJVWZ` |  |
| 2098 | L2 = L1 + Pu2O3 |  | experimental | [1] Guéneau 2008; _cites Martin 1969_ | Table 3, p. 9, row 4; `ORC-DY46LRYZYI` |  |
| 2098 | L2 = L1 + Pu2O3 |  | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 5; `ORC-QVCDNDQMZY` |  |
| 1450 | polymorphic: PuO2-x = PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333; PuO1.61: O 0.616858, Pu 0.383142 | experimental | [1] Guéneau 2008; _cites Besmann 1987_ [doi](https://doi.org/10.1016/0022-3115%2887%2990289-3) | Table 3, p. 9, row 19; `ORC-QPUCAQJYMY` |  |
| 1450 | polymorphic: PuO2-x = PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333; PuO1.61: O 0.616858, Pu 0.383142 | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 20; `ORC-RXDFPA6FXA` |  |
| 1445 | polymorphic: PuO2-x = PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 21; `ORC-A3FTYN6VTF` |  |
| 1422 | PuO2-x = Pu2O3 + PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 24; `ORC-5NL2ZA52JU` |  |
| 1353 | PuO2-x = Pu2O3 + PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Besmann 1987_ [doi](https://doi.org/10.1016/0022-3115%2887%2990289-3) | Table 3, p. 9, row 22; `ORC-RJEDYGQGMF` |  |
| 1353 | PuO2-x = Pu2O3 + PuO1.61 | PuO2-x: O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 23; `ORC-Z7QEIIIY4S` |  |
| 987 | PuO2(2) = PuO1.61 + PuO2(1) | PuO2(2): O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 39; `ORC-MOBCWNUP6X` |  |
| 943 | PuO2(2) = PuO1.61 + PuO2(1) | PuO2(2): O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Boivineau 1976_ [doi](https://doi.org/10.1016/0022-3115%2876%2990114-8) | Table 3, p. 9, row 36; `ORC-47CIGYUNCJ` |  |
| 912 | L = ε-Pu + Pu2O3 |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 40; `ORC-ANHX4AGPUB` |  |
| 903 | PuO2(2) = PuO1.61 + PuO2(1) | PuO2(2): O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Sari 1968_ | Table 3, p. 9, row 37; `ORC-KNUVPHZXMX` |  |
| 903 | PuO2(2) = PuO1.61 + PuO2(1) | PuO2(2): O 0.666667, Pu 0.333333 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 38; `ORC-PWQV22YLRI` |  |
| 756 | polymorphic: ε-Pu = δ′-Pu |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 41; `ORC-L6KJZQISIJ` |  |
| 743 | PuO1.52 = Pu2O3 + PuO1.61 | PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Sari 1968_ | Table 3, p. 9, row 27; `ORC-EOLVRLQDKM` |  |
| 736 | polymorphic: δ′-Pu = δ-Pu |  | model | [1] Guéneau 2008 | Table 3, p. 9, row 42; `ORC-E2VHOARLNR` |  |
| 723 | PuO1.52 = Pu2O3 + PuO1.61 | PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 28; `ORC-GIMHAIKOAT` |  |
| 711 | PuO1.52 = Pu2O3 + PuO1.61 | PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 29; `ORC-MILSFKL3VZ` |  |
| 623 | PuO1.52 = Pu2O3 + PuO1.61 | PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Gardner 1965_ [doi](https://doi.org/10.1016/0022-1902%2865%2980259-7) | Table 3, p. 9, row 26; `ORC-FTNAAL2GIZ` |  |
| 608 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Sari 1968_ | Table 3, p. 9, row 33; `ORC-D2WSPO4WHQ` |  |
| 608 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | unspecified | [1] Guéneau 2008; _cites Wriedt 1990_ [doi](https://doi.org/10.1007/bf02841705) | Table 3, p. 9, row 34; `ORC-NMCSFIROZH` |  |
| 576 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | model | [1] Guéneau 2008 | Table 3, p. 9, row 35; `ORC-GT6QHGEZO6` |  |
| 573 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Boivineau 1976_ [doi](https://doi.org/10.1016/0022-3115%2876%2990114-8) | Table 3, p. 9, row 32; `ORC-3IYINHT7VJ` |  |
| 573 | PuO1.52 = Pu2O3 + PuO1.61 | PuO1.52: O 0.603175, Pu 0.396825; PuO1.61: O 0.616858, Pu 0.383142 | experimental | [1] Guéneau 2008; _cites Boivineau 1976_ [doi](https://doi.org/10.1016/0022-3115%2876%2990114-8) | Table 3, p. 9, row 25; `ORC-I4MSG3JTZ2` |  |
| 573 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Chikalla 1964_ [doi](https://doi.org/10.1016/0022-3115%2864%2990132-1) | Table 3, p. 9, row 30; `ORC-JPUM4P7MAN` |  |
| 573 | PuO1.61 = PuO1.52 + PuO2 | PuO1.61: O 0.616858, Pu 0.383142 (basis unresolved); PuO1.52: O 0.603175, Pu 0.396825 (basis unresolved); PuO2: O 0.666667, Pu 0.333333 (basis unresolved) | experimental | [1] Guéneau 2008; _cites Gardner 1965_ [doi](https://doi.org/10.1016/0022-1902%2865%2980259-7) | Table 3, p. 9, row 31; `ORC-XJK2LTNYWQ` |  |

## 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–Pu system (18)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -337 kJ/mol-atom ± 5 | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008; _cites Markin 1966_ | Table 5, p. 12, row 5; `ORC-T2HFJI5UOJ.f8a95c` |  |
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -334 kJ/mol-atom ± 4 | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008; _cites Glushko 1982_ | Table 5, p. 12, row 6; `ORC-GFASNJZHCC.2aad51` |  |
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -331.24 kJ/mol-atom | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008 | Table 5, p. 12, row 1; `ORC-LWEXDRW5FQ.b063b7` |  |
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -331.2 kJ/mol-atom | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008; _cites Besmann 1987_ [doi](https://doi.org/10.1016/0022-3115%2887%2990289-3) | Table 5, p. 12, row 3; `ORC-SENC6YVBRT` |  |
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -331.2 kJ/mol-atom ± 2 | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 7; `ORC-VU2ABEKVOK.2f612b` |  |
| Pu2O3 | [Pu2O3](https://data.orchid-project.org/compounds/Pu2O3.html) | -330.8 kJ/mol-atom ± 4 | 298.15 | model | -328.25 (mp-aaaabfrz) | -350.52 (oqmd-12710) | [1] Guéneau 2008; _cites Chereau 1977_ [doi](https://doi.org/10.1016/0021-9614%2877%2990040-4) | Table 5, p. 12, row 4; `ORC-IDGMWCWEQD.54dec8` |  |
| PuO1,52 |  | -335.317 kJ/mol-atom ± 3.96825 | 298.15 | model |  |  | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 9; `ORC-BQ7EBIS6BA.4474ae` |  |
| PuO1,52 |  | -332.54 kJ/mol-atom | 298.15 | model |  |  | [1] Guéneau 2008 | Table 5, p. 12, row 8; `ORC-EBMTXVKTB3.dc77b1` |  |
| PuO1,61 |  | -342.912 kJ/mol-atom ± 2.29885 | 298.15 | model |  |  | [1] Guéneau 2008; _cites Markin 1966_ | Table 5, p. 12, row 11; `ORC-IW4K2IGBVB.07daca` |  |
| PuO1,61 |  | -338.889 kJ/mol-atom ± 6.39847 | 298.15 | model |  |  | [1] Guéneau 2008; _cites Chereau 1977_ [doi](https://doi.org/10.1016/0021-9614%2877%2990040-4) | Table 5, p. 12, row 12; `ORC-O2MKQDICEJ.012a44` |  |
| PuO1,61 |  | -335.441 kJ/mol-atom ± 3.83142 | 298.15 | model |  |  | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 13; `ORC-QX5Z74ABJL.0e15ad` |  |
| PuO1,61 |  | -332.261 kJ/mol-atom | 298.15 | model |  |  | [1] Guéneau 2008 | Table 5, p. 12, row 10; `ORC-3UQSOYYDZ5.ba5118` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -353.433 kJ/mol-atom | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008 | Table 5, p. 12, row 14; `ORC-GDXU3MPORQ.1fe2e7` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -352.667 kJ/mol-atom ± 0.533333 | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008; _cites Holley 1958_ | Table 5, p. 12, row 16; `ORC-5YUIRMEX4S.3fe5f1` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -352 kJ/mol-atom ± 1.33333 | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008; _cites Popov 1957_ [doi](https://doi.org/10.1007/bf01489634) | Table 5, p. 12, row 15; `ORC-FPCN67JW5P.3dc6bb` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -351.933 kJ/mol-atom ± 0.266667 | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008; _cites Glushko 1982_ | Table 5, p. 12, row 19; `ORC-ZNNFD6KEAX.1512be` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -351.933 kJ/mol-atom ± 0.333333 | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 20; `ORC-ZXLORLKZVH.0fa640` |  |
| PuO2 | [PuO2](https://data.orchid-project.org/compounds/PuO2.html) | -351.9 kJ/mol-atom ± 0.24 | 298.15 | model | -352.148 (mp-aaaaacxj) | -314.622 (oqmd-6102) | [1] Guéneau 2008; _cites Johnson 1969_ [doi](https://doi.org/10.1016/0021-9614%2869%2990039-1) | Table 5, p. 12, row 17; `ORC-FJ53JQFDQ6.53c4e2` |  |

## Other properties

### Phase transition (2)

Table: Phase transition, O–Pu system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 17.65 K | 17.65 | other | experimental | [1] Guéneau 2008; _cites Flotow 1981_ [doi](https://doi.org/10.1063/1.441691) | p. 4; `ORC-ZS5EGKB22K` | “For the Pu2O3 compound, determinations of the heat capacity at low temperature by Flotow et al. \[41\] (including a k transition at 17.65 K) led to an entropy value at 298 K as compiled by Glushko et al. \[42\] and Lemire et al. \[43\] and retained in the SGTE data bank \[44\].” |
| Phase transition | 2358 K | 2358 | Pu2O3 | experimental | [1] Guéneau 2008 | p. 4; `ORC-LNG6SF4QF7` | “Glushko estimated the high temperature heat capacity by comparison with PuO2(s) (using a Cp ratio 1.7 from 350 K to the melting temperature 2358 K).” |

### Heat capacity / entropy / enthalpy (22)

Table: Heat capacity / entropy / enthalpy, O–Pu system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: S (298.15 K)_ | 32.6 J/mol-atom/K | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Glushko 1982_ | Table 5, p. 12, row 6; `ORC-GFASNJZHCC.4f31a2` |  |
| Entropy; _printed: S (298.15 K)_ | 31.88 J/mol-atom/K ± 5.02 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Chereau 1977_ [doi](https://doi.org/10.1016/0021-9614%2877%2990040-4) | Table 5, p. 12, row 4; `ORC-IDGMWCWEQD.e9ceea` |  |
| Entropy; _printed: S (298.15 K)_ | 32.68 J/mol-atom/K | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 1; `ORC-LWEXDRW5FQ.6fea97` |  |
| Entropy; _printed: S (298.15 K)_ | 28.44 J/mol-atom/K ± 4.18 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Markin 1966_ | Table 5, p. 12, row 5; `ORC-T2HFJI5UOJ.aea71c` |  |
| Entropy; _printed: S (298.15 K)_ | 32.6 J/mol-atom/K ± 0.12 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 7; `ORC-VU2ABEKVOK.09c9f8` |  |
| Entropy; _printed: S (298.15 K)_ | 32.64 J/mol-atom/K ± 0.12 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Flotow 1981_ [doi](https://doi.org/10.1063/1.441691) | Table 5, p. 12, row 2; `ORC-ZTIH5QJ4FR.2f7511` |  |
| Entropy; _printed: S (298.15 K)_ | 31.9048 J/mol-atom/K | 298.15 | PuO1,52; _alloy: O 0.603175, Pu 0.396825_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 8; `ORC-EBMTXVKTB3.2fca80` |  |
| Entropy; _printed: S (298.15 K)_ | 31.1111 J/mol-atom/K | 298.15 | PuO1,61; _alloy: O 0.616858, Pu 0.383142_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 10; `ORC-3UQSOYYDZ5.7953e9` |  |
| Entropy; _printed: S (298.15 K)_ | 30.7663 J/mol-atom/K ± 4.02299 | 298.15 | PuO1,61; _alloy: O 0.616858, Pu 0.383142_ | model | [1] Guéneau 2008; _cites Markin 1966_ | Table 5, p. 12, row 11; `ORC-IW4K2IGBVB.4695a2` |  |
| Entropy; _printed: S (298.15 K)_ | 33.3333 J/mol-atom/K ± 6.39847 | 298.15 | PuO1,61; _alloy: O 0.616858, Pu 0.383142_ | model | [1] Guéneau 2008; _cites Chereau 1977_ [doi](https://doi.org/10.1016/0021-9614%2877%2990040-4) | Table 5, p. 12, row 12; `ORC-O2MKQDICEJ.1b990c` |  |
| Entropy; _printed: S (298.15 K)_ | 31.8008 J/mol-atom/K ± 1.91571 | 298.15 | PuO1,61; _alloy: O 0.616858, Pu 0.383142_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 13; `ORC-QX5Z74ABJL.48d6f5` |  |
| Entropy; _printed: S (298.15 K)_ | 22.0433 J/mol-atom/K ± 0.1 | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008; _cites Flotow 1981_ [doi](https://doi.org/10.1063/1.441691) | Table 5, p. 12, row 18; `ORC-FHXHVDNJPC.609ee9` |  |
| Entropy; _printed: S (298.15 K)_ | 22.0433 J/mol-atom/K | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 14; `ORC-GDXU3MPORQ.e569c2` |  |
| Entropy; _printed: S (298.15 K)_ | 22.0433 J/mol-atom/K | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008; _cites Glushko 1982_ | Table 5, p. 12, row 19; `ORC-ZNNFD6KEAX.128244` |  |
| Entropy; _printed: S (298.15 K)_ | 22.0433 J/mol-atom/K ± 0.0866667 | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 20; `ORC-ZXLORLKZVH.17603b` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 23.4 J/mol-atom/K | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 1; `ORC-LWEXDRW5FQ.28cd23` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 23.4 J/mol-atom/K ± 0.1 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 7; `ORC-VU2ABEKVOK.0bcae7` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 23.4 J/mol-atom/K ± 0.1 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | model | [1] Guéneau 2008; _cites Flotow 1981_ [doi](https://doi.org/10.1063/1.441691) | Table 5, p. 12, row 2; `ORC-ZTIH5QJ4FR.2f42cd` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 23.4483 J/mol-atom/K ± 1.91571 | 298.15 | PuO1,61; _alloy: O 0.616858, Pu 0.383142_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 13; `ORC-QX5Z74ABJL.8b0d06` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 22.08 J/mol-atom/K | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008; _cites Flotow 1981_ [doi](https://doi.org/10.1063/1.441691) | Table 5, p. 12, row 18; `ORC-FHXHVDNJPC.371307` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 22.0833 J/mol-atom/K | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008 | Table 5, p. 12, row 14; `ORC-GDXU3MPORQ.8f2c71` |  |
| Heat capacity; _printed: Cp (298.15 K)_ | 22.0833 J/mol-atom/K ± 0.0866667 | 298.15 | PuO2; _alloy: Pu 0.333333_ | model | [1] Guéneau 2008; _cites Lemire 2001_ | Table 5, p. 12, row 20; `ORC-ZXLORLKZVH.1f1a1b` |  |

### Crystal structure (5)

Table: Crystal structure, O–Pu system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a | 0.3838 not_printed ± 1.000e-4 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | experimental | [1] Guéneau 2008; _cites Wulff 1988_ [doi](https://doi.org/10.1063/1.454935) | Table 1, p. 2, row 7; `ORC-YBPMNCP4GL.b90c5a` |  |
| Lattice a | 1.1045 not_printed | 298.15 | PuO1.52; _alloy: Pu 0.396825_ | experimental | [1] Guéneau 2008; _cites Boivineau 1976_ [doi](https://doi.org/10.1016/0022-3115%2876%2990114-8) | Table 1, p. 2, row 8; `ORC-7PONBQHROV` |  |
| Lattice a | 1.0991 not_printed | 298.15 | PuO1.61; _alloy: Pu 0.383142_ | experimental | [1] Guéneau 2008; _cites Sari 1968_ | Table 1, p. 2, row 9; `ORC-EGZY2XVU2W` |  |
| Lattice a | 0.53955 not_printed | 298.15 | PuO2; _alloy: Pu 0.333333_ | experimental | [1] Guéneau 2008; _cites Taylor 1984_ | Table 1, p. 2, row 10; `ORC-OYWDVQFCR2` |  |
| Lattice c | 0.5918 not_printed ± 1.000e-4 | 298.15 | Pu2O3; _alloy: Pu 0.4_ | experimental | [1] Guéneau 2008; _cites Wulff 1988_ [doi](https://doi.org/10.1063/1.454935) | Table 1, p. 2, row 7; `ORC-YBPMNCP4GL.d35490` |  |

## Sources

Reporting papers the values were read from (a value cited from another work names that work in its row).

1. Christine Guéneau, Christian Chatillon, Bo Sundman, Thermodynamic modelling of the plutonium–oxygen system, Journal of Nuclear Materials 378, 257-272 (2008). [doi:10.1016/j.jnucmat.2008.06.013](https://doi.org/10.1016/j.jnucmat.2008.06.013)

## 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=\<id>, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).