O–Pd phases

7 phases (tier A 4, liquid 1, gas 2); 0 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–Pd system page · Markdown · field reference

Phases of the O–Pd system (7)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
BCC_A2 phase:o-pd:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	no calculated diagram	0	1
FCC_A1 phase:o-pd:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	no calculated diagram	0	1
GAS phase:o-pd:gas	gas	gas	no calculated diagram	0	1
HCP_A3 phase:o-pd:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	no calculated diagram	0	1
ION phase:o-pd:ion	liquid	liquid	no calculated diagram	0	1
O2GAS phase:o-pd:o2gas	gas	gas	no calculated diagram	0	1
PDO_B17 phase:o-pd:pdo-b17	PtS · B17 · tP4 · P4_2/mmc (131)	tier A: standard phase name	no calculated diagram	18	1

BCC_A2 (O–Pd)

Id: phase:o-pd:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stoichiometry: Pd 1.0000
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:bcc-a2
tdb: tdb:PdO-22Lau.tdb:BCC_A2

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

PdO-22Lau.tdb: BCC_A2, type code %B, sha256 2a4381b59d9a9254…

38: PHASE BCC_A2 %B 2 1 3 !
39: CONST BCC_A2 : PD : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

FCC_A1 (O–Pd)

Id: phase:o-pd:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:fcc-a1
tdb: tdb:PdO-22Lau.tdb:FCC_A1

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

PdO-22Lau.tdb: FCC_A1, type code %A, sha256 2a4381b59d9a9254…

33: PHASE FCC_A1 %A 2 1 1 !
34: CONST FCC_A1 : PD : O VA% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

GAS (O–Pd)

Id: phase:o-pd:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:gas
tdb: tdb:PdO-22Lau.tdb:GAS

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

PdO-22Lau.tdb: GAS, type code %, sha256 2a4381b59d9a9254…

54: PHASE GAS:G % 1 1 !
55: CONST GAS:G : O O2 O3 PD : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

HCP_A3 (O–Pd)

Id: phase:o-pd:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
Stoichiometry: Pd 1.0000
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:hcp-a3
tdb: tdb:PdO-22Lau.tdb:HCP_A3

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

PdO-22Lau.tdb: HCP_A3, type code %A, sha256 2a4381b59d9a9254…

43: PHASE HCP_A3 %A 2 1 0.5 !
44: CONST HCP_A3 : PD : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

ION (O–Pd)

Id: phase:o-pd:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:ion
tdb: tdb:PdO-22Lau.tdb:ION

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

PdO-22Lau.tdb: ION, type code %, sha256 2a4381b59d9a9254…

28: PHASE ION:Y % 2 1 1 !
29: CONST ION:Y : PD+2 : O-2 VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

O2GAS (O–Pd)

Id: phase:o-pd:o2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: no calculated diagram
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:o-pd:o2gas
tdb: tdb:PdO-22Lau.tdb:O2GAS

TDB models of O2GAS (1): PHASE and CONSTITUENT statements as written

PdO-22Lau.tdb: O2GAS, type code %, sha256 2a4381b59d9a9254…

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

Example references (1 of 1; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase

PDO_B17 (O–Pd)

Id: phase:o-pd:pdo-b17; status assigned
Structure: PtS · B17 · tP4 · P4_2/mmc (131); type st:b17-pts-tp4; tier A: standard phase name; confidence high
Stability: no calculated diagram
Literature: 18 values (0 accepted) from 1 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:o-pd:pdo-b17
paper: paper:10.1016/j.jct.2022.106831:PdO
tdb: tdb:PdO-22Lau.tdb:PDO_B17

TDB models of PDO_B17 (1): PHASE and CONSTITUENT statements as written

PdO-22Lau.tdb: PDO_B17, type code %, sha256 2a4381b59d9a9254…

48: PHASE PDO_B17:I % 2 1 1 !
49: CONST PDO_B17:I : PD+2 : O-2 : !

Example references (10 of 11; assessments first):

doi:10.1016/j.jct.2022.106831 C. Laurin, A. Quaini, E. Regnier, A. Laplace, T. Croze, S. Gossé, The metallic palladium-rhodium solution in interaction with oxygen: The Pd-Rh-O phase diagram and thermodynamics, The Journal of Chemical Thermodynamics 172, 106831 (2022).
assessment that models this phase; reports values for this phase
doi:10.1149/1.2426509 J. Stuart Warner, The Free Energy of Formation of Palladium Oxide, J. Electrochem. Soc. 114, 68 (1967).
cited as the source of values for this phase
doi:10.1016/0016-7037(96)00115-9 J. Nell, H.St.C. O'Neill, Gibbs free energy of formation and heat capacity of PdO: A new calibration of the PdPdO buffer to high temperatures and pressures, Geochimica et Cosmochimica Acta 60, 2487-2493 (1996).
cited as the source of values for this phase
doi:10.1007/bf00613213 J. Fouletier, G. Vitter, M. Kleitz, Measurement and regulation of oxygen content in gases using solid electrolyte cells. III. Oxygen pump-gauge, J Appl Electrochem 5, 111-120 (1975).
cited as the source of values for this phase
doi:10.1016/0022-5088(83)90516-7 C. Mallika, O.M. Sreedharan, J.B. Gnanamoorthy, Determination of the standard free energy of formation of PdO(s) from the solid oxide electrolyte e.m.f., Journal of the Less Common Metals 95, 213-220 (1983).
cited as the source of values for this phase
doi:10.1016/0040-6031(75)80040-2 G. Bayer, H.G. Wiedemann, Formation, dissociation and expansion behavior of platinum group metal oxides (PdO, RuO2, IrO2), Thermochimica Acta 11, 79-88 (1975).
cited as the source of values for this phase
doi:10.1021/j100883a502 Wayne E. Bell, R. E. Inyard, M. Tagami, Dissociation of Palladium Oxide<sup>1</sup>, J. Phys. Chem. 70, 3735-3736 (1966).
cited as the source of values for this phase
doi:10.1361/105497198770342076 K. T. Jacob, S. Priya, Y. Waseda, Thermodynamic mixing properties and solid-state immiscibility in the systems Pd-Rh and Pd-Rh-O, JPE 19, 340-350 (1998).
cited as the source of values for this phase
doi:10.1361/105497199770340545 K. T. Jacob, T. H. Okabe, T. Uda, Y. Waseda, System Nd-Pd-O: Phase diagram and thermodynamic properties of oxides using a solid-state cell with advanced features, JPE 20, 553-564 (1999).
cited as the source of values for this phase
doi:10.1524/zpch.1964.41.1_2.078 Norbert G. Schmahl, Erich Minzl, Die thermische Zersetzung des Rhodium(III)-oxids und deren Beeinflussung durch Legierungsbildung mit Platin und Palladium, Zeitschrift für Physikalische Chemie 41, 78-96 (1964).
cited as the source of values for 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}
}