H–Mg phases

6 phases (tier A 4, liquid 1, gas 1); 4 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 · H–Mg system page · Markdown · field reference

Phases of the H–Mg system (6)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
BCC_A2 phase:h-mg:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	not stable in 2 calculated diagram(s)	0	2
FCC_A1 phase:h-mg:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 2 calculated diagram(s)	0	2
GAS phase:h-mg:gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–2500 K, x(H) 0–1	11	2
HCP_A3 phase:h-mg:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–922.82 K, x(H) 0–0.00072	11	2
LIQUID phase:h-mg:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 922.77–1367.51 K, x(H) 0–0.00158	4	2
MGH2_C4 phase:h-mg:mgh2-c4	TiO2 · C4 · tP6 · P4_2/mnm (136)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–561.44 K, x(H) 0.66667–0.66667	9	2

BCC_A2 (H–Mg)

Id: phase:h-mg:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stoichiometry: Mg 1.0000
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-mg:bcc-a2
tdb: tdb:MgH-07Pal.tdb:BCC_A2, tdb:MgH-99Zen.tdb:BCC_A2

TDB models of BCC_A2 (2): PHASE and CONSTITUENT statements as written

MgH-07Pal.tdb: BCC_A2, type code %B, sha256 8871b1dc6e5850f7…

37: PHASE BCC_A2 %B 2 1 3 !
38: CONST BCC_A2 : MG : VA : !

MgH-99Zen.tdb: BCC_A2, type code %B, sha256 7133dff29673a4f1…

37: PHASE BCC_A2 %B 2 1 3 !
38: CONST BCC_A2 : MG : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
assessment that models this phase
doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase

FCC_A1 (H–Mg)

Id: phase:h-mg:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stoichiometry: Mg 1.0000
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:h-mg:fcc-a1
tdb: tdb:MgH-07Pal.tdb:FCC_A1, tdb:MgH-99Zen.tdb:FCC_A1

TDB models of FCC_A1 (2): PHASE and CONSTITUENT statements as written

MgH-07Pal.tdb: FCC_A1, type code %A, sha256 8871b1dc6e5850f7…

32: PHASE FCC_A1 %A 2 1 1 !
33: CONST FCC_A1 : MG : VA : !

MgH-99Zen.tdb: FCC_A1, type code %A, sha256 7133dff29673a4f1…

32: PHASE FCC_A1 %A 2 1 1 !
33: CONST FCC_A1 : MG : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
assessment that models this phase
doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase

GAS (H–Mg)

Id: phase:h-mg:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–2500 K, x(H) 0–1
Literature: 11 values (11 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:h-mg:gas
paper: paper:10.1016/s0360-3199(98)00132-3:gas
tdb: tdb:MgH-07Pal.tdb:GAS, tdb:MgH-99Zen.tdb:GAS

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

MgH-07Pal.tdb: GAS, type code %, sha256 8871b1dc6e5850f7…

50: PHASE GAS:G % 1 1 !
51: CONST GAS:G : H H2 MG MG2 MGH : !

MgH-99Zen.tdb: GAS, type code %, sha256 7133dff29673a4f1…

50: PHASE GAS:G % 1 1 !
51: CONST GAS:G : H H2 MG MG2 MGH : !

Example references (2 of 2; assessments first):

doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
assessment that models this phase

HCP_A3 (H–Mg)

Id: phase:h-mg: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: stable in 2 of 2 calculated diagram(s): 300–922.82 K, x(H) 0–0.00072
Literature: 11 values (11 accepted) from 1 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:h-mg:hcp-a3
paper: paper:10.1016/s0360-3199(98)00132-3:(Mg)
tdb: tdb:MgH-07Pal.tdb:HCP_A3, tdb:MgH-99Zen.tdb:HCP_A3

TDB models of HCP_A3 (2): PHASE and CONSTITUENT statements as written

MgH-07Pal.tdb: HCP_A3, type code %A, sha256 8871b1dc6e5850f7…

42: PHASE HCP_A3 %A 2 1 0.5 !
43: CONST HCP_A3 : MG : H VA% : !

MgH-99Zen.tdb: HCP_A3, type code %A, sha256 7133dff29673a4f1…

42: PHASE HCP_A3 %A 2 1 0.5 !
43: CONST HCP_A3 : MG : H VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
assessment that models this phase

LIQUID (H–Mg)

Id: phase:h-mg:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 922.77–1367.51 K, x(H) 0–0.00158
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:h-mg:liquid
paper: paper:10.1016/s0360-3199(98)00132-3:L, paper:10.1016/s0360-3199(98)00132-3:Liquid
tdb: tdb:MgH-07Pal.tdb:LIQUID, tdb:MgH-99Zen.tdb:LIQUID

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

MgH-07Pal.tdb: LIQUID, type code %, sha256 8871b1dc6e5850f7…

27: PHASE LIQUID:L % 1 1 !
28: CONST LIQUID:L : H MG : !

MgH-99Zen.tdb: LIQUID, type code %, sha256 7133dff29673a4f1…

27: PHASE LIQUID:L % 1 1 !
28: CONST LIQUID:L : H MG : !

Example references (2 of 2; assessments first):

doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
assessment that models this phase

MGH2_C4 (H–Mg)

Id: phase:h-mg:mgh2-c4; status assigned
Structure: TiO2 · C4 · tP6 · P4_2/mnm (136); type st:c4-tio2-tp6; tier A: standard phase name; confidence high
Caveat: DFT agrees: on-hull mp-aaaabjby and oqmd-3742, space group 136
Stoichiometry: H 0.6667, Mg 0.3333
Stability: stable in 2 of 2 calculated diagram(s): 300–561.44 K, x(H) 0.66667–0.66667
Literature: 9 values (9 accepted) from 1 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:h-mg:mgh2-c4
mp: mp:mp-aaaabjby
oqmd: oqmd:oqmd-3742
paper: paper:10.1016/s0360-3199(98)00132-3:MgH2
tdb: tdb:MgH-07Pal.tdb:MGH2_C4, tdb:MgH-99Zen.tdb:MGH2_C4

TDB models of MGH2_C4 (2): PHASE and CONSTITUENT statements as written

MgH-07Pal.tdb: MGH2_C4, type code %, sha256 8871b1dc6e5850f7…

47: PHASE MGH2_C4 % 2 1 2 !
48: CONST MGH2_C4 : MG : H : !

MgH-99Zen.tdb: MGH2_C4, type code %, sha256 7133dff29673a4f1…

47: PHASE MGH2_C4 % 2 1 2 !
48: CONST MGH2_C4 : MG : H : !

Example references (2 of 2; assessments first):

doi:10.1016/S0360-3199(98)00132-3 K. Zeng, T. Klassen, W. Oelerich, R. Bormann, Int. J. Hydrogen Energy, 24, 989-1004(1999).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2007.04.005 M. Palumbo, F.J. Torres, J.R. Ares, C. Pisani, J.F. Fernandez, M. Baricco, Thermodynamic and ab initio investigation of the Al–H–Mg system, Calphad 31, 457-467 (2007).
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}
}