Mo–Ta phases

5 phases (tier A 4, liquid 1); 3 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 · Mo–Ta system page · Markdown · field reference

Phases of the Mo–Ta system (5)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
BCC_A2 phase:mo-ta:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 6 of 6 calculated diagram(s): 300–4000 K, x(Ta) 0–1	0	8
B2_BCC phase:mo-ta:bcc-b2	CsCl · B2 · cP2 · Pm-3m (221)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–3280 K, x(Ta) 0.07–0.97	0	2
FCC_A1 phase:mo-ta:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 6 calculated diagram(s)	0	6
HCP_A3 phase:mo-ta:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 6 calculated diagram(s)	0	6
LIQUID phase:mo-ta:liquid	liquid	liquid	stable in 6 of 6 calculated diagram(s): 2853.04–4000 K, x(Ta) 0–1	11	6

BCC_A2 (Mo–Ta)

Id: phase:mo-ta:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stability: stable in 6 of 6 calculated diagram(s): 300–4000 K, x(Ta) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (9): corpus: corpus:phase:mo-ta:bcc-a2
tdb: tdb:MoTa-04Xio.tdb:BCC_A2, tdb:MoTa-05Tur.tdb:A2_BCC, tdb:MoTa-05Tur.tdb:BCC_A2, tdb:MoTa-20Raj.tdb:BCC_A2, tdb:MoTa-22Zha.tdb:A2_BCC, tdb:MoTa-22Zha.tdb:BCC_A2, tdb:MoTa-91Kau-LB.tdb:BCC_A2, tdb:MoTa-99Cui.tdb:BCC_A2

TDB models of BCC_A2 (8): PHASE and CONSTITUENT statements as written

MoTa-04Xio.tdb: BCC_A2, type code %B, sha256 92183b3959627078…

35: PHASE BCC_A2 %B 2 1 3 !
36: CONST BCC_A2 : MO% TA% : VA : !

MoTa-05Tur.tdb: A2_BCC, type code %B, sha256 88917f2b0afc92ac…

39: PHASE A2_BCC %B 2 1 3 !
40: CONST A2_BCC : MO TA : VA : !

MoTa-05Tur.tdb: BCC_A2, type code %B, sha256 88917f2b0afc92ac…

34: PHASE BCC_A2 %B 2 1 3 !
35: CONST BCC_A2 : MO% TA% : VA : !

MoTa-20Raj.tdb: BCC_A2, type code %B, sha256 cfa37cba21b8d3df…

35: PHASE BCC_A2 %B 2 1 3 !
36: CONST BCC_A2 : MO% TA% : VA : !

MoTa-22Zha.tdb: A2_BCC, type code %B, sha256 a89e2ac4995bb46b…

46: PHASE A2_BCC %B 2 1 3 !
47: CONST A2_BCC : MO TA : VA : !

MoTa-22Zha.tdb: BCC_A2, type code %B, sha256 a89e2ac4995bb46b…

41: PHASE BCC_A2 %B 2 1 3 !
42: CONST BCC_A2 : MO% TA% : VA : !

MoTa-91Kau-LB.tdb: BCC_A2, type code %B, sha256 7885146f2baf656f…

30: PHASE BCC_A2 %B 2 1 3 !
31: CONST BCC_A2 : MO% TA% : VA : !

MoTa-99Cui.tdb: BCC_A2, type code %B, sha256 1ea55690b63df718…

30: PHASE BCC_A2 %B 2 1 3 !
31: CONST BCC_A2 : MO% TA% : VA : !

Example references (6 of 6; assessments first):

doi:10.1007/s11661-999-0110-0 Yuwen Cui, Zhanpeng Jin, Xiaogang Lu, Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system, Metall Mater Trans A 30, 2735-2744 (1999).
assessment that models this phase
doi:10.1016/0364-5916(91)90004-4 Lany Kaufman, Coupled thermochemical and phase diagram data for tantalum based binary alloys, Calphad 15, 243-259 (1991).
assessment that models this phase
doi:10.1016/j.calphad.2004.07.002 W. Xiong, Y. Du, Y. Liu, B.Y. Huang, H.H. Xu, H.L. Chen, Z. Pan, Calphad, 28, 133-40(2004).
assessment that models this phase
doi:10.1016/j.ijrmhm.2020.105335 V.B. Rajkumar, Yong Du, Shuhong Liu, Kaiming Cheng, Ajeet Kumar Srivastav, Measurements of the melting points, liquidus, and solidus of the Mo, Ta, and Mo Ta binary alloys using a novel high-speed pyrometric technique, International Journal of Refractory Metals and Hard Materials 93, 105335 (2020).
assessment that models this phase
doi:10.1016/j.ijrmhm.2022.105780 Enkuan Zhang, Ying Tang, Mingwen Wen, Abdulmonem Obaied, Irina Roslyakova, Lijun Zhang, On phase stability of Mo-Nb-Ta-W refractory high entropy alloys, International Journal of Refractory Metals and Hard Materials 103, 105780 (2022).
assessment that models this phase
doi:10.1103/PhysRevB.71.094206 P.E.A. Turchi, V. Drchal, J. Kudrnovsky, C. Colinet, L. Kaufman, Z.-K. Liu, Phys. Rev. B, 71, 094206(2005).
assessment that models this phase

B2_BCC (Mo–Ta)

Id: phase:mo-ta:bcc-b2; status assigned
Structure: CsCl · B2 · cP2 · Pm-3m (221); type st:b2-cscl-cp2; tier A: standard phase name; confidence high
Caveat: MoTa-05Tur.tdb: ordered phase with disordered part A2_BCC (order/disorder model)
Caveat: MoTa-22Zha.tdb: ordered phase with disordered part A2_BCC (order/disorder model)
Caveat: partitioned order/disorder model in MoTa-05Tur.tdb also describes the disordered state
Caveat: partitioned order/disorder model in MoTa-22Zha.tdb also describes the disordered state
Stability: stable in 2 of 2 calculated diagram(s): 300–3280 K, x(Ta) 0.07–0.97
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:mo-ta:bcc-b2
tdb: tdb:MoTa-05Tur.tdb:B2_BCC, tdb:MoTa-22Zha.tdb:B2_BCC

TDB models of B2_BCC (2): PHASE and CONSTITUENT statements as written

MoTa-05Tur.tdb: B2_BCC, type code %BO, sha256 88917f2b0afc92ac…

44: PHASE B2_BCC %BO 3 0.5 0.5 3 !
45: CONST B2_BCC : MO TA : MO TA : VA : !

MoTa-22Zha.tdb: B2_BCC, type code %BO, sha256 a89e2ac4995bb46b…

51: PHASE B2_BCC %BO 3 0.5 0.5 3 !
52: CONST B2_BCC : MO TA : MO TA : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.ijrmhm.2022.105780 Enkuan Zhang, Ying Tang, Mingwen Wen, Abdulmonem Obaied, Irina Roslyakova, Lijun Zhang, On phase stability of Mo-Nb-Ta-W refractory high entropy alloys, International Journal of Refractory Metals and Hard Materials 103, 105780 (2022).
assessment that models this phase
doi:10.1103/PhysRevB.71.094206 P.E.A. Turchi, V. Drchal, J. Kudrnovsky, C. Colinet, L. Kaufman, Z.-K. Liu, Phys. Rev. B, 71, 094206(2005).
assessment that models this phase

FCC_A1 (Mo–Ta)

Id: phase:mo-ta:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stability: not stable in 6 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (7): corpus: corpus:phase:mo-ta:fcc-a1
tdb: tdb:MoTa-04Xio.tdb:FCC_A1, tdb:MoTa-05Tur.tdb:FCC_A1, tdb:MoTa-20Raj.tdb:FCC_A1, tdb:MoTa-22Zha.tdb:FCC_A1, tdb:MoTa-91Kau-LB.tdb:FCC_A1, tdb:MoTa-99Cui.tdb:FCC_A1

TDB models of FCC_A1 (6): PHASE and CONSTITUENT statements as written

MoTa-04Xio.tdb: FCC_A1, type code %A, sha256 92183b3959627078…

30: PHASE FCC_A1 %A 2 1 1 !
31: CONST FCC_A1 : MO TA : VA : !

MoTa-05Tur.tdb: FCC_A1, type code %A, sha256 88917f2b0afc92ac…

29: PHASE FCC_A1 %A 2 1 1 !
30: CONST FCC_A1 : MO TA : VA : !

MoTa-20Raj.tdb: FCC_A1, type code %A, sha256 cfa37cba21b8d3df…

30: PHASE FCC_A1 %A 2 1 1 !
31: CONST FCC_A1 : MO TA : VA : !

MoTa-22Zha.tdb: FCC_A1, type code %A, sha256 a89e2ac4995bb46b…

36: PHASE FCC_A1 %A 2 1 1 !
37: CONST FCC_A1 : MO TA : VA : !

MoTa-91Kau-LB.tdb: FCC_A1, type code %A, sha256 7885146f2baf656f…

25: PHASE FCC_A1 %A 2 1 1 !
26: CONST FCC_A1 : MO TA : VA : !

MoTa-99Cui.tdb: FCC_A1, type code %A, sha256 1ea55690b63df718…

25: PHASE FCC_A1 %A 2 1 1 !
26: CONST FCC_A1 : MO TA : VA : !

Example references (6 of 6; assessments first):

doi:10.1007/s11661-999-0110-0 Yuwen Cui, Zhanpeng Jin, Xiaogang Lu, Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system, Metall Mater Trans A 30, 2735-2744 (1999).
assessment that models this phase
doi:10.1016/0364-5916(91)90004-4 Lany Kaufman, Coupled thermochemical and phase diagram data for tantalum based binary alloys, Calphad 15, 243-259 (1991).
assessment that models this phase
doi:10.1016/j.calphad.2004.07.002 W. Xiong, Y. Du, Y. Liu, B.Y. Huang, H.H. Xu, H.L. Chen, Z. Pan, Calphad, 28, 133-40(2004).
assessment that models this phase
doi:10.1016/j.ijrmhm.2020.105335 V.B. Rajkumar, Yong Du, Shuhong Liu, Kaiming Cheng, Ajeet Kumar Srivastav, Measurements of the melting points, liquidus, and solidus of the Mo, Ta, and Mo Ta binary alloys using a novel high-speed pyrometric technique, International Journal of Refractory Metals and Hard Materials 93, 105335 (2020).
assessment that models this phase
doi:10.1016/j.ijrmhm.2022.105780 Enkuan Zhang, Ying Tang, Mingwen Wen, Abdulmonem Obaied, Irina Roslyakova, Lijun Zhang, On phase stability of Mo-Nb-Ta-W refractory high entropy alloys, International Journal of Refractory Metals and Hard Materials 103, 105780 (2022).
assessment that models this phase
doi:10.1103/PhysRevB.71.094206 P.E.A. Turchi, V. Drchal, J. Kudrnovsky, C. Colinet, L. Kaufman, Z.-K. Liu, Phys. Rev. B, 71, 094206(2005).
assessment that models this phase

HCP_A3 (Mo–Ta)

Id: phase:mo-ta:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
Stability: not stable in 6 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (7): corpus: corpus:phase:mo-ta:hcp-a3
tdb: tdb:MoTa-04Xio.tdb:HCP_A3, tdb:MoTa-05Tur.tdb:HCP_A3, tdb:MoTa-20Raj.tdb:HCP_A3, tdb:MoTa-22Zha.tdb:HCP_A3, tdb:MoTa-91Kau-LB.tdb:HCP_A3, tdb:MoTa-99Cui.tdb:HCP_A3

TDB models of HCP_A3 (6): PHASE and CONSTITUENT statements as written

MoTa-04Xio.tdb: HCP_A3, type code %A, sha256 92183b3959627078…

40: PHASE HCP_A3 %A 2 1 0.5 !
41: CONST HCP_A3 : MO TA : VA : !

MoTa-05Tur.tdb: HCP_A3, type code %A, sha256 88917f2b0afc92ac…

49: PHASE HCP_A3 %A 2 1 0.5 !
50: CONST HCP_A3 : MO TA : VA : !

MoTa-20Raj.tdb: HCP_A3, type code %A, sha256 cfa37cba21b8d3df…

40: PHASE HCP_A3 %A 2 1 0.5 !
41: CONST HCP_A3 : MO TA : VA : !

MoTa-22Zha.tdb: HCP_A3, type code %A, sha256 a89e2ac4995bb46b…

56: PHASE HCP_A3 %A 2 1 0.5 !
57: CONST HCP_A3 : MO TA : VA : !

MoTa-91Kau-LB.tdb: HCP_A3, type code %A, sha256 7885146f2baf656f…

35: PHASE HCP_A3 %A 2 1 0.5 !
36: CONST HCP_A3 : MO TA : VA : !

MoTa-99Cui.tdb: HCP_A3, type code %A, sha256 1ea55690b63df718…

35: PHASE HCP_A3 %A 2 1 0.5 !
36: CONST HCP_A3 : MO TA : VA : !

Example references (6 of 6; assessments first):

doi:10.1007/s11661-999-0110-0 Yuwen Cui, Zhanpeng Jin, Xiaogang Lu, Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system, Metall Mater Trans A 30, 2735-2744 (1999).
assessment that models this phase
doi:10.1016/0364-5916(91)90004-4 Lany Kaufman, Coupled thermochemical and phase diagram data for tantalum based binary alloys, Calphad 15, 243-259 (1991).
assessment that models this phase
doi:10.1016/j.calphad.2004.07.002 W. Xiong, Y. Du, Y. Liu, B.Y. Huang, H.H. Xu, H.L. Chen, Z. Pan, Calphad, 28, 133-40(2004).
assessment that models this phase
doi:10.1016/j.ijrmhm.2020.105335 V.B. Rajkumar, Yong Du, Shuhong Liu, Kaiming Cheng, Ajeet Kumar Srivastav, Measurements of the melting points, liquidus, and solidus of the Mo, Ta, and Mo Ta binary alloys using a novel high-speed pyrometric technique, International Journal of Refractory Metals and Hard Materials 93, 105335 (2020).
assessment that models this phase
doi:10.1016/j.ijrmhm.2022.105780 Enkuan Zhang, Ying Tang, Mingwen Wen, Abdulmonem Obaied, Irina Roslyakova, Lijun Zhang, On phase stability of Mo-Nb-Ta-W refractory high entropy alloys, International Journal of Refractory Metals and Hard Materials 103, 105780 (2022).
assessment that models this phase
doi:10.1103/PhysRevB.71.094206 P.E.A. Turchi, V. Drchal, J. Kudrnovsky, C. Colinet, L. Kaufman, Z.-K. Liu, Phys. Rev. B, 71, 094206(2005).
assessment that models this phase

LIQUID (Mo–Ta)

Id: phase:mo-ta:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 6 of 6 calculated diagram(s): 2853.04–4000 K, x(Ta) 0–1
Literature: 11 values (11 accepted) from 1 papers
Interactive: phase registry entry

Names (8): corpus: corpus:phase:mo-ta:liquid
paper: paper:10.1016/j.ijrmhm.2020.105335:liquid
tdb: tdb:MoTa-04Xio.tdb:LIQUID, tdb:MoTa-05Tur.tdb:LIQUID, tdb:MoTa-20Raj.tdb:LIQUID, tdb:MoTa-22Zha.tdb:LIQUID, tdb:MoTa-91Kau-LB.tdb:LIQUID, tdb:MoTa-99Cui.tdb:LIQUID

TDB models of LIQUID (6): PHASE and CONSTITUENT statements as written

MoTa-04Xio.tdb: LIQUID, type code %, sha256 92183b3959627078…

25: PHASE LIQUID:L % 1 1 !
26: CONST LIQUID:L : MO TA : !

MoTa-05Tur.tdb: LIQUID, type code %, sha256 88917f2b0afc92ac…

24: PHASE LIQUID:L % 1 1 !
25: CONST LIQUID:L : MO TA : !

MoTa-20Raj.tdb: LIQUID, type code %, sha256 cfa37cba21b8d3df…

25: PHASE LIQUID:L % 1 1 !
26: CONST LIQUID:L : MO TA : !

MoTa-22Zha.tdb: LIQUID, type code %, sha256 a89e2ac4995bb46b…

31: PHASE LIQUID:L % 1 1 !
32: CONST LIQUID:L : MO TA : !

MoTa-91Kau-LB.tdb: LIQUID, type code %, sha256 7885146f2baf656f…

20: PHASE LIQUID:L % 1 1 !
21: CONST LIQUID:L : MO TA : !

MoTa-99Cui.tdb: LIQUID, type code %, sha256 1ea55690b63df718…

20: PHASE LIQUID:L % 1 1 !
21: CONST LIQUID:L : MO TA : !

Example references (6 of 6; assessments first):

doi:10.1016/j.ijrmhm.2020.105335 V.B. Rajkumar, Yong Du, Shuhong Liu, Kaiming Cheng, Ajeet Kumar Srivastav, Measurements of the melting points, liquidus, and solidus of the Mo, Ta, and Mo Ta binary alloys using a novel high-speed pyrometric technique, International Journal of Refractory Metals and Hard Materials 93, 105335 (2020).
assessment that models this phase; reports values for this phase
doi:10.1007/s11661-999-0110-0 Yuwen Cui, Zhanpeng Jin, Xiaogang Lu, Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system, Metall Mater Trans A 30, 2735-2744 (1999).
assessment that models this phase
doi:10.1016/0364-5916(91)90004-4 Lany Kaufman, Coupled thermochemical and phase diagram data for tantalum based binary alloys, Calphad 15, 243-259 (1991).
assessment that models this phase
doi:10.1016/j.calphad.2004.07.002 W. Xiong, Y. Du, Y. Liu, B.Y. Huang, H.H. Xu, H.L. Chen, Z. Pan, Calphad, 28, 133-40(2004).
assessment that models this phase
doi:10.1016/j.ijrmhm.2022.105780 Enkuan Zhang, Ying Tang, Mingwen Wen, Abdulmonem Obaied, Irina Roslyakova, Lijun Zhang, On phase stability of Mo-Nb-Ta-W refractory high entropy alloys, International Journal of Refractory Metals and Hard Materials 103, 105780 (2022).
assessment that models this phase
doi:10.1103/PhysRevB.71.094206 P.E.A. Turchi, V. Drchal, J. Kudrnovsky, C. Colinet, L. Kaufman, Z.-K. Liu, Phys. Rev. B, 71, 094206(2005).
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}
}