Cu–O phases

10 phases (tier A 3, tier C 3, liquid 2, gas 2); 7 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 · Cu–O system page · Markdown · field reference

Phases of the Cu–O system (10)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
BCC_A2 phase:cu-o:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	not stable in 3 calculated diagram(s)	0	5
CUPRITE_C3 phase:cu-o:c3-cuprite	Cu2O · C3 · cP6 · Pn-3m (224)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 3 of 3 calculated diagram(s): 300–1094.79 K, x(O) 0.33333–0.33333	84	5
CU4O3 phase:cu-o:cu4o3	Cu4O3 · tI28 · I4_1/amd (141)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	not stable in 2 calculated diagram(s)	0	3
CUO phase:cu-o:cuo	CuO · B26 · mC8 · C2/c (15)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 3 of 3 calculated diagram(s): 300–416 K, x(O) 0.5–0.5	76	5
FCC_A1 phase:cu-o:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–1357.77 K, x(O) 0–1	0	5
GAS phase:cu-o:gas	gas	gas	stable in 3 of 3 calculated diagram(s): 1382.32–2500 K, x(O) 0.92505–1	0	5
HCP_A3 phase:cu-o:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 3 calculated diagram(s)	0	5
ION phase:cu-o:ion	liquid	liquid	stable in 1 of 1 calculated diagram(s): 1342.77–2500 K, x(O) 0–0.39143	0	3
LIQUID phase:cu-o:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 1342.77–2500 K, x(O) 0–0.39158	18	2
O2GAS phase:cu-o:o2gas	gas	gas	stable in 2 of 3 calculated diagram(s): 300–416 K, x(O) 1–1	0	5

BCC_A2 (Cu–O)

Id: phase:cu-o:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stoichiometry: Cu 1.0000
Stability: not stable in 3 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:bcc-a2
tdb: tdb:CuO-03Hal-LB.tdb:BCC_A2, tdb:CuO-05Sch.tdb:BCC_A2, tdb:CuO-14Mag.tdb:BCC_A2, tdb:CuO-92Bou.tdb:BCC_A2, tdb:CuO-94Hal.tdb:BCC_A2

TDB models of BCC_A2 (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: BCC_A2, type code %B, sha256 5836249ea0179639…

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

CuO-05Sch.tdb: BCC_A2, type code %B, sha256 a3dbcda00b2b888e…

48: PHASE BCC_A2 %B 2 1 3 !
49: CONST BCC_A2 : CU : VA : !

CuO-14Mag.tdb: BCC_A2, type code %B, sha256 c359243f81916348…

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

CuO-92Bou.tdb: BCC_A2, type code %B, sha256 01c48e87b93fb30f…

49: PHASE BCC_A2 %B 2 1 3 !
50: CONST BCC_A2 : CU : VA : !

CuO-94Hal.tdb: BCC_A2, type code %B, sha256 59102ffec95449e3…

45: PHASE BCC_A2 %B 2 1 3 !
46: CONST BCC_A2 : CU : VA : !

Example references (5 of 5; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase

CUPRITE_C3 (Cu–O)

Id: phase:cu-o:c3-cuprite; status assigned
Structure: Cu2O · C3 · cP6 · Pn-3m (224); type st:c3-cu2o-cp6; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (unrecognised_name_tokens:CUPRITE); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: stable in 3 of 3 calculated diagram(s): 300–1094.79 K, x(O) 0.33333–0.33333
Literature: 84 values (84 accepted) from 1 papers
Interactive: phase registry entry

Names (8): corpus: corpus:phase:cu-o:c3-cuprite, corpus:phase:cu-o:cuprite-c3
paper: paper:10.1007/bf02649399:Cu2O
tdb: tdb:CuO-03Hal-LB.tdb:CUPRITE_C3, tdb:CuO-05Sch.tdb:CUPRITE_C3, tdb:CuO-14Mag.tdb:CUPRITE_C3, tdb:CuO-92Bou.tdb:CUPRITE_C3, tdb:CuO-94Hal.tdb:CUPRITE_C3

TDB models of CUPRITE_C3 (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: CUPRITE_C3, type code %, sha256 5836249ea0179639…

57: PHASE CUPRITE_C3:I % 2 2 1 !
58: CONST CUPRITE_C3:I : CU+1 : O-2 : !

CuO-05Sch.tdb: CUPRITE_C3, type code %, sha256 a3dbcda00b2b888e…

58: PHASE CUPRITE_C3:I % 2 2 1 !
59: CONST CUPRITE_C3:I : CU+1 : O-2 : !

CuO-14Mag.tdb: CUPRITE_C3, type code %, sha256 c359243f81916348…

57: PHASE CUPRITE_C3:I % 2 2 1 !
58: CONST CUPRITE_C3:I : CU+1 : O-2 : !

CuO-92Bou.tdb: CUPRITE_C3, type code %, sha256 01c48e87b93fb30f…

59: PHASE CUPRITE_C3:I % 2 2 1 !
60: CONST CUPRITE_C3:I : CU+1 : O-2 : !

CuO-94Hal.tdb: CUPRITE_C3, type code %, sha256 59102ffec95449e3…

55: PHASE CUPRITE_C3:I % 2 2 1 !
56: CONST CUPRITE_C3:I : CU+1 : O-2 : !

Example references (10 of 16; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase
doi:10.1002/srin.197003613 Wilhelm Anton Fischer, Gerd Pateisky, Die Eignung fester Metall-Metalloxid-Gemische als Bezugspotentiale in Sauerstoffmeßzellen, Archiv für das Eisenhüttenwesen 41, 661-673 (1970).
cited as the source of values for this phase
doi:10.1007/bf00639610 H. Peters, G. Mann, Elektrochemische Untersuchung der Reduktionsgleichgewichte von Metalloxyden, Naturwissenschaften 45, 209-209 (1958).
cited as the source of values for this phase
doi:10.1007/bf02654367 Rainer Schmid, A thermodynamic analysis of the Cu-O system with an associated solution model, Metall Trans B 14, 473-481 (1983).
cited as the source of values for this phase
doi:10.1016/0021-9614(79)90145-9 N. Kemori, I. Katayama, Z. Kozuka, Measurements of standard molar Gibbs energies of formation of NiO, Cu2O, and CoO from solid and liquid metals and oxygen gas by an e.m.f. method at high temperatures, The Journal of Chemical Thermodynamics 11, 215-228 (1979).
cited as the source of values for this phase
doi:10.1016/0022-5088(85)90079-7 C Mallika, O.M Sreedharan, M.S Chandrasekharaiah, Determination of the standard Gibbs energy of formation of Rh2O3(s) and IrO2(s) from solid oxide electrolyte electromotive force measurements, Journal of the Less Common Metals 107, 203-212 (1985).
cited as the source of values for this phase

CU4O3 (Cu–O)

Id: phase:cu-o:cu4o3; status assigned
Structure: Cu4O3 · tI28 · I4_1/amd (141); type st:cu4o3-ti28; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (no_structure_token, off_stoichiometric_model); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:cu-o:cu4o3
tdb: tdb:CuO-03Hal-LB.tdb:CU4O3, tdb:CuO-14Mag.tdb:CU4O3, tdb:CuO-94Hal.tdb:CU4O3

TDB models of CU4O3 (3): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: CU4O3, type code %, sha256 5836249ea0179639…

67: PHASE CU4O3:I % 3 2 2 3 !
68: CONST CU4O3:I : CU+1 : CU+2 : O-2 : !

CuO-14Mag.tdb: CU4O3, type code %, sha256 c359243f81916348…

67: PHASE CU4O3:I % 3 2 2 3 !
68: CONST CU4O3:I : CU+1 : CU+2 : O-2 : !

CuO-94Hal.tdb: CU4O3, type code %, sha256 59102ffec95449e3…

65: PHASE CU4O3:I % 3 2 2 3 !
66: CONST CU4O3:I : CU+1 : CU+2 : O-2 : !

Example references (3 of 3; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase

CUO (Cu–O)

Id: phase:cu-o:cuo; status assigned
Structure: CuO · B26 · mC8 · C2/c (15); type st:b26-cuo-mc8; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (no_structure_token, off_stoichiometric_model); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: stable in 3 of 3 calculated diagram(s): 300–416 K, x(O) 0.5–0.5
Literature: 76 values (70 accepted) from 2 papers
Interactive: phase registry entry

Names (8): corpus: corpus:phase:cu-o:cuo
paper: paper:10.1007/bf02649399:CuO, paper:10.1361/154770305x74421:CuO
tdb: tdb:CuO-03Hal-LB.tdb:CUO, tdb:CuO-05Sch.tdb:CUO, tdb:CuO-14Mag.tdb:CUO, tdb:CuO-92Bou.tdb:CUO, tdb:CuO-94Hal.tdb:CUO

TDB models of CUO (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: CUO, type code %, sha256 5836249ea0179639…

62: PHASE CUO % 2 1 1 !
63: CONST CUO : CU+2 : O-2 : !

CuO-05Sch.tdb: CUO, type code %, sha256 a3dbcda00b2b888e…

63: PHASE CUO % 2 1 1 !
64: CONST CUO : CU+2 : O-2 : !

CuO-14Mag.tdb: CUO, type code %, sha256 c359243f81916348…

62: PHASE CUO % 2 1 1 !
63: CONST CUO : CU+2 : O-2 : !

CuO-92Bou.tdb: CUO, type code %, sha256 01c48e87b93fb30f…

64: PHASE CUO:I % 2 1 1 !
65: CONST CUO:I : CU+2 : O-2 : !

CuO-94Hal.tdb: CUO, type code %, sha256 59102ffec95449e3…

60: PHASE CUO % 2 1 1 !
61: CONST CUO : CU+2 : O-2 : !

Example references (10 of 15; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase; reports values for this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase
doi:10.1021/ja01438a009 H. S. Roberts, F. Hastings Smyth, THE SYSTEM COPPER: CUPRIC OXIDE: OXYGEN., J. Am. Chem. Soc. 43, 1061-1079 (1921).
cited as the source of values for this phase
doi:10.1007/bf02654367 Rainer Schmid, A thermodynamic analysis of the Cu-O system with an associated solution model, Metall Trans B 14, 473-481 (1983).
cited as the source of values for this phase
doi:10.1021/ja01106a056 Jih-Heng Hu, Herrick L. Johnston, Low Temperature Heat Capacities of Inorganic Solids. XVI. Heat Capacity of Cupric Oxide from 15 to 300 °K.<sup>1</sup>, J. Am. Chem. Soc. 75, 2471-2473 (1953).
cited as the source of values for this phase
doi:10.1002/hlca.19440270195 W. Feitknecht, Über die Löslichkeitsprodukte der Oxyde und des Hydroxyds von Kupfer und über die Löslichkeit von Kupferhydroxyd in Natronlauge, Helvetica Chimica Acta 27, 771-775 (1944).
cited as the source of values for this phase
doi:10.1002/hlca.19650480528 P. Schindler, H. Althaus, F. Hofer, W. Minder, Löslichkeitsprodukte von Metalloxiden und ‐hydroxiden. 10. Mitteilung. Löslichkeitsprodukte von Zinkoxid, Kupferhydroxid und Kupferoxid in Abhängigkeit von Teilchengrösse und molarer Oberfläche. Ein Beitrag zur Thermodynamik von Grenzflächen fest‐flüssig, Helvetica Chimica Acta 48, 1204-1215 (1965).
cited as the source of values for this phase

FCC_A1 (Cu–O)

Id: phase:cu-o:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 300–1357.77 K, x(O) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:fcc-a1
tdb: tdb:CuO-03Hal-LB.tdb:FCC_A1, tdb:CuO-05Sch.tdb:FCC_A1, tdb:CuO-14Mag.tdb:FCC_A1, tdb:CuO-92Bou.tdb:FCC_A1, tdb:CuO-94Hal.tdb:FCC_A1

TDB models of FCC_A1 (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: FCC_A1, type code %A, sha256 5836249ea0179639…

42: PHASE FCC_A1 %A 2 1 1 !
43: CONST FCC_A1 : CU : VA% O : !

CuO-05Sch.tdb: FCC_A1, type code %A, sha256 a3dbcda00b2b888e…

43: PHASE FCC_A1 %A 2 1 1 !
44: CONST FCC_A1 : CU% O : VA : !

CuO-14Mag.tdb: FCC_A1, type code %A, sha256 c359243f81916348…

42: PHASE FCC_A1 %A 2 1 1 !
43: CONST FCC_A1 : CU : VA% O : !

CuO-92Bou.tdb: FCC_A1, type code %A, sha256 01c48e87b93fb30f…

44: PHASE FCC_A1 %A 2 1 1 !
45: CONST FCC_A1 : CU% O : VA : !

CuO-94Hal.tdb: FCC_A1, type code %A, sha256 59102ffec95449e3…

40: PHASE FCC_A1 %A 2 1 1 !
41: CONST FCC_A1 : CU% O : VA : !

Example references (5 of 5; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase

GAS (Cu–O)

Id: phase:cu-o:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 1382.32–2500 K, x(O) 0.92505–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:gas
tdb: tdb:CuO-03Hal-LB.tdb:GAS, tdb:CuO-05Sch.tdb:GAS, tdb:CuO-14Mag.tdb:GAS, tdb:CuO-92Bou.tdb:GAS, tdb:CuO-94Hal.tdb:GAS

TDB models of GAS (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: GAS, type code %, sha256 5836249ea0179639…

73: PHASE GAS:G % 1 1 !
74: CONST GAS:G : CU CUO O O2 O3 : !

CuO-05Sch.tdb: GAS, type code %, sha256 a3dbcda00b2b888e…

69: PHASE GAS:G % 1 1 !
70: CONST GAS:G : CU CUO O O2 O3 : !

CuO-14Mag.tdb: GAS, type code %, sha256 c359243f81916348…

73: PHASE GAS:G % 1 1 !
74: CONST GAS:G : CU CU2 CUO O O2 O3 : !

CuO-92Bou.tdb: GAS, type code %, sha256 01c48e87b93fb30f…

70: PHASE GAS:G % 1 1 !
71: CONST GAS:G : CU CU2 CUO O O2 O3 : !

CuO-94Hal.tdb: GAS, type code %, sha256 59102ffec95449e3…

71: PHASE GAS:G % 1 1 !
72: CONST GAS:G : CU CUO O O2 O3 : !

Example references (5 of 5; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase

HCP_A3 (Cu–O)

Id: phase:cu-o: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: Cu 1.0000
Stability: not stable in 3 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:hcp-a3
tdb: tdb:CuO-03Hal-LB.tdb:HCP_A3, tdb:CuO-05Sch.tdb:HCP_A3, tdb:CuO-14Mag.tdb:HCP_A3, tdb:CuO-92Bou.tdb:HCP_A3, tdb:CuO-94Hal.tdb:HCP_A3

TDB models of HCP_A3 (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: HCP_A3, type code %A, sha256 5836249ea0179639…

52: PHASE HCP_A3 %A 2 1 0.5 !
53: CONST HCP_A3 : CU : VA : !

CuO-05Sch.tdb: HCP_A3, type code %A, sha256 a3dbcda00b2b888e…

53: PHASE HCP_A3 %A 2 1 0.5 !
54: CONST HCP_A3 : CU : VA : !

CuO-14Mag.tdb: HCP_A3, type code %A, sha256 c359243f81916348…

52: PHASE HCP_A3 %A 2 1 0.5 !
53: CONST HCP_A3 : CU : VA : !

CuO-92Bou.tdb: HCP_A3, type code %A, sha256 01c48e87b93fb30f…

54: PHASE HCP_A3 %A 2 1 0.5 !
55: CONST HCP_A3 : CU : VA : !

CuO-94Hal.tdb: HCP_A3, type code %A, sha256 59102ffec95449e3…

50: PHASE HCP_A3 %A 2 1 0.5 !
51: CONST HCP_A3 : CU : VA : !

Example references (5 of 5; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase

ION (Cu–O)

Id: phase:cu-o:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 1342.77–2500 K, x(O) 0–0.39143
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:cu-o:ion
tdb: tdb:CuO-03Hal-LB.tdb:ION, tdb:CuO-05Sch.tdb:ION, tdb:CuO-94Hal.tdb:ION

TDB models of ION (3): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: ION, type code %, sha256 5836249ea0179639…

37: PHASE ION:Y % 2 1 1 !
38: CONST ION:Y : CU+1 CU+2 : O-2 VA : !

CuO-05Sch.tdb: ION, type code %, sha256 a3dbcda00b2b888e…

38: PHASE ION:Y % 2 1 1 !
39: CONST ION:Y : CU+1 CU+2 CU+3 : O-2 VA : !

CuO-94Hal.tdb: ION, type code %, sha256 59102ffec95449e3…

35: PHASE ION:Y % 2 1 1 !
36: CONST ION:Y : CU+1 CU+2 : O-2 VA : !

Example references (3 of 3; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase

LIQUID (Cu–O)

Id: phase:cu-o:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 1342.77–2500 K, x(O) 0–0.39158
Literature: 18 values (16 accepted) from 2 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:liquid
paper: paper:10.1007/bf02649399:L2, paper:10.1007/bf02649399:liquid, paper:10.1361/154770305x74421:liquid
tdb: tdb:CuO-14Mag.tdb:LIQUID, tdb:CuO-92Bou.tdb:LIQUID

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

CuO-14Mag.tdb: LIQUID, type code %, sha256 c359243f81916348…

37: PHASE LIQUID:L % 1 1 !
38: CONST LIQUID:L : CU CU2O O : !

CuO-92Bou.tdb: LIQUID, type code %, sha256 01c48e87b93fb30f…

39: PHASE LIQUID:L % 1 1 !
40: CONST LIQUID:L : CU CU2O O : !

Example references (10 of 10; assessments first):

doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
assessment that models this phase
doi:10.1007/bf02649399 B. Hallstedt, D. Risold, L. J. Gauckler, Thermodynamic assessment of the copper-oxygen system, JPE 15, 483-499 (1994).
reports values for this phase
doi:10.1361/154770305x74421 L. Schramm, G. Behr, W. Löser, K. Wetzig, Thermodynamic Reassessment of the Cu-O Phase Diagram, Journal of Phase Equilibria & Diffusion 26, 605-612 (2005).
reports values for this phase
doi:10.1007/bf02654367 Rainer Schmid, A thermodynamic analysis of the Cu-O system with an associated solution model, Metall Trans B 14, 473-481 (1983).
cited as the source of values for this phase
doi:10.1021/ja01438a009 H. S. Roberts, F. Hastings Smyth, THE SYSTEM COPPER: CUPRIC OXIDE: OXYGEN., J. Am. Chem. Soc. 43, 1061-1079 (1921).
cited as the source of values for this phase
doi:10.1098/rspa.1912.0107 R. E. Slade, F. D. Farrow, An investigation of the dissociation pressures and melting points of the system Copper-cuprous oxide, Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character 87, 524-534 (1912).
cited as the source of values for this phase
doi:10.1515/ijmr-1968-590711 J. Gerlach, J. Osterwald, and W. Stichel,"Coulometric Determination of the Miscibility Gap between Liquid Copper and Copper(I) Oxide,"Z. Metallkd., 59(7), 576-579 (1968) in German.
cited as the source of values for this phase
doi:10.2320/jinstmet1952.42.5_527 Y. Kayahara, K. Ono, T. Oishi, and J. Moriyama, "Thermodynamic Study of the Liquid Cu-O System," Trans. Jpn. Inst. Met., 22(7), 493-500 (1981); Y. Kayahara, K. Ono, T. Oishi, and J. Moriyama, "Thermodynamic Study of the Liquid Cu-O System," J. Jpn. Inst. Met.,42(5), 527-533 (1978) in Japanese. 8lOts: S. Otsuka and Z. Kozuka, "Activities of Oxygen in Liquid Copper and Silver from Electrochemical Me
cited as the source of values for this phase
doi:10.2320/matertrans1960.21.275 Nobumasa Kemori, Iwao Katayama, Zensaku Kozuka, Thermodynamic Study of Oxygen in Liquid Copper, Trans. JIM 21, 275-284 (1980).
cited as the source of values for this phase

O2GAS (Cu–O)

Id: phase:cu-o:o2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 3 calculated diagram(s): 300–416 K, x(O) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:cu-o:o2gas
tdb: tdb:CuO-03Hal-LB.tdb:O2GAS, tdb:CuO-05Sch.tdb:O2GAS, tdb:CuO-14Mag.tdb:O2GAS, tdb:CuO-92Bou.tdb:O2GAS, tdb:CuO-94Hal.tdb:O2GAS

TDB models of O2GAS (5): PHASE and CONSTITUENT statements as written

CuO-03Hal-LB.tdb: O2GAS, type code %, sha256 5836249ea0179639…

70: PHASE O2GAS % 1 1 !
71: CONST O2GAS : O2 :!

CuO-05Sch.tdb: O2GAS, type code %, sha256 a3dbcda00b2b888e…

66: PHASE O2GAS % 1 1 !
67: CONST O2GAS : O2 :!

CuO-14Mag.tdb: O2GAS, type code %, sha256 c359243f81916348…

70: PHASE O2GAS % 1 1 !
71: CONST O2GAS : O2 :!

CuO-92Bou.tdb: O2GAS, type code %, sha256 01c48e87b93fb30f…

67: PHASE O2GAS % 1 1 !
68: CONST O2GAS : O2 :!

CuO-94Hal.tdb: O2GAS, type code %, sha256 59102ffec95449e3…

68: PHASE O2GAS % 1 1 !
69: CONST O2GAS : O2 :!

Example references (5 of 5; assessments first):

doi:10.1007/BF02649399 B. Hallstedt, D. Risold and L.J. Gauckler, J. Phase Equilib., 15, 483-99(1994).
assessment that models this phase
doi:10.1016/j.calphad.2014.09.004 Hans Magnusson, Karin Frisk, Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures, Calphad 47, 148-160 (2014).
assessment that models this phase
doi:10.1016/S0364-5916(03)00050-6 B. Hallstedt, L.J. Gauckler, Calphad, 27, 177-91(2003).
assessment that models this phase
doi:10.1361/154770305X74421 J. Phase Equilib. Diffus., 26, 605-12(2005).
assessment that models this phase
doi:10.1515/ijmr-1992-830905 A. Boudene, K. Hack, A. Mohammad, D. Neuschuetz, E. Zimmermann, Z. Metallkd., 83, 663-68(1992).
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}
}