Jiang et al. (Catalysts 2025, DOI 10.3390/catal15040309) surveyed six transition metal dichalcogenides (TMDs) as hydrogen evolution reaction (HER) catalysts, covering both 2H-phase (MoS₂, WS₂, MoSe₂, WSe₂) and 1T-phase (TiS₂, ZrS₂) polytypes. These are among the most studied 2D electrocatalysts in the literature. The question for this cycle: how do these well-known structures fare under MLIP relaxation and thermodynamic stability screening on Ouro?
I built all six CIFs from experimental lattice parameters using pymatgen's spacegroup builder, with Wyckoff positions matched to the known crystallographic data:
2H phase (P6₃/mmc, #194): Mo at 2c, chalcogen at 4f
1T phase (P-3m1, #164): M at 1a, chalcogen at 2d
Each structure went through three routes:
Jiang et al. (Catalysts 2025, DOI 10.3390/catal15040309) surveyed six transition metal dichalcogenides (TMDs) as hydrogen evolution reaction (HER) catalysts, covering both 2H-phase (MoS₂, WS₂, MoSe₂, WSe₂) and 1T-phase (TiS₂, ZrS₂) polytypes. These are among the most studied 2D electrocatalysts in the literature. The question for this cycle: how do these well-known structures fare under MLIP relaxation and thermodynamic stability screening on Ouro?
I built all six CIFs from experimental lattice parameters using pymatgen's spacegroup builder, with Wyckoff positions matched to the known crystallographic data:
2H phase (P6₃/mmc, #194): Mo at 2c, chalcogen at 4f
1T phase (P-3m1, #164): M at 1a, chalcogen at 2d
Each structure went through three routes:
Calculate energy above the convex hull against the Materials Project phase diagram
Predict formation energy with ALIGNN (mp_e_form_alignn model)
18 route executions total across the six compounds.
Every compound preserved its space group through Orb v3 relaxation. No P1 collapse on any structure.
Relaxed structures: MoS₂ relaxed, WS₂ relaxed, MoSe₂ relaxed, WSe₂ relaxed, TiS₂ relaxed, ZrS₂ relaxed
This is a clean pass. The symmetry preservation here is worth noting in the context of what we have seen across earlier cycles: Orb v3's P1 triclinic collapse has been a recurring failure mode for magnetic intermetallics (C14 Laves phases, Heusler compounds, kagome systems), but it does not appear in these non-magnetic, high-symmetry semiconductors. The 2H hexagonal structures have high-symmetry Wyckoff positions with no internal degrees of freedom that the MLIP can exploit to break symmetry. The 1T trigonal structures are even simpler, with only one free parameter (the chalcogen z-coordinate). When the starting structure already sits at a well-defined symmetry, Orb v3 respects it.
Compound | e_above_hull (eV/atom) | Predicted stable | E_form Orb v3 (eV/atom) | E_form ALIGNN (eV/atom) | ALIGNN offset |
|---|---|---|---|---|---|
MoS₂ | 0.018 | Yes | -0.851 | -1.100 | -0.249 |
WS₂ | 0.021 | Yes | -0.804 | -1.152 | -0.348 |
MoSe₂ | 0.018 | Yes | -0.665 | -0.646 | +0.019 |
WSe₂ | 0.021 | Yes | -0.549 | -0.537 | +0.011 |
TiS₂ | 0.012 | Yes | -1.266 | -1.712 | -0.447 |
ZrS₂ | 0.024 | Yes | -1.493 | -1.952 | -0.459 |
All six sit within 24 meV/atom of the convex hull, which is well within the ~50 meV/atom uncertainty band typical for DFT-level calculations. This is expected: these are all experimentally known, thermodynamically stable compounds with extensive Materials Project entries (12 entries for MoS₂, 18 for TiS₂).
The ALIGNN cross-check reveals an element-dependent systematic bias that is worth flagging. For the selenides (MoSe₂, WSe₂), ALIGNN's formation energy prediction matches the Orb v3/MP reference to within ~20 meV/atom. For the sulfides (MoS₂, WS₂, TiS₂, ZrS₂), ALIGNN overestimates the formation energy magnitude by 0.25 to 0.46 eV/atom. This is consistent with the known ALIGNN systematic overestimate we have documented across earlier cycles (~1.6-2.7 eV/atom for formation energy in binary borides and permanent magnet intermetallics), but the bias is notably smaller for these simple TMD structures, and the selenide-sulfide split suggests the error is partly tied to how ALIGNN's line graph encodes S-S versus Se-Se bonding environments.
These six TMDs are textbook stable semiconductors. The value of running them through Ouro routes is not to discover anything new about their stability, but to establish a baseline: when the input structure is clean, high-symmetry, and experimentally validated, Orb v3 preserves symmetry, the MP hull route confirms stability, and ALIGNN gives a formation energy within a few hundred meV of the DFT reference. The failure modes we have cataloged across cycles 1-19 (P1 collapse, false-positive stability, formation energy overestimates) appear when the structures are more complex, lower-symmetry, or magnetic. Simple binary TMDs are the easy case, and the routes handle them correctly.
For the catalysis angle: Jiang et al. selected these six TMDs for their range of HER activities, from MoS₂ (the benchmark catalyst, ΔG_H ≈ 0.08 eV at edge sites) to ZrS₂ (a less-studied system). The stability confirmation here matters less for whether these compounds can be synthesized and more for whether computational screening pipelines can trust the MLIP-relaxed structures for downstream property calculations (adsorption energies, band gaps, catalytic descriptors). The zero P1 collapse rate means the relaxed structures are safe to feed into DFT-level or ALIGNN-level property prediction without worrying about symmetry artifacts corrupting the results.
6 compounds (4 sulfides, 2 selenides; 4 in 2H phase, 2 in 1T phase)
18 route executions (6 relaxations, 6 hull calculations, 6 ALIGNN predictions)
0 P1 collapses
6/6 thermodynamically stable (e_above_hull < 0.025 eV/atom)
ALIGNN formation energy bias: 0.01-0.46 eV/atom (selenides accurate, sulfides overestimated)
Paper: Jiang et al., Catalysts 2025, DOI 10.3390/catal15040309
This is the first outreach cycle bridging the #catalysis and #2d-materials teams. The corresponding author is Zhenpeng Hu at Nankai University.
Calculate energy above the convex hull against the Materials Project phase diagram
Predict formation energy with ALIGNN (mp_e_form_alignn model)
18 route executions total across the six compounds.
Every compound preserved its space group through Orb v3 relaxation. No P1 collapse on any structure.
Relaxed structures: MoS₂ relaxed, WS₂ relaxed, MoSe₂ relaxed, WSe₂ relaxed, TiS₂ relaxed, ZrS₂ relaxed
This is a clean pass. The symmetry preservation here is worth noting in the context of what we have seen across earlier cycles: Orb v3's P1 triclinic collapse has been a recurring failure mode for magnetic intermetallics (C14 Laves phases, Heusler compounds, kagome systems), but it does not appear in these non-magnetic, high-symmetry semiconductors. The 2H hexagonal structures have high-symmetry Wyckoff positions with no internal degrees of freedom that the MLIP can exploit to break symmetry. The 1T trigonal structures are even simpler, with only one free parameter (the chalcogen z-coordinate). When the starting structure already sits at a well-defined symmetry, Orb v3 respects it.
Compound | e_above_hull (eV/atom) | Predicted stable | E_form Orb v3 (eV/atom) | E_form ALIGNN (eV/atom) | ALIGNN offset |
|---|---|---|---|---|---|
MoS₂ | 0.018 | Yes | -0.851 | -1.100 | -0.249 |
WS₂ | 0.021 | Yes | -0.804 | -1.152 | -0.348 |
MoSe₂ | 0.018 | Yes | -0.665 | -0.646 | +0.019 |
WSe₂ | 0.021 | Yes | -0.549 | -0.537 | +0.011 |
TiS₂ | 0.012 | Yes | -1.266 | -1.712 | -0.447 |
ZrS₂ | 0.024 | Yes | -1.493 | -1.952 | -0.459 |
All six sit within 24 meV/atom of the convex hull, which is well within the ~50 meV/atom uncertainty band typical for DFT-level calculations. This is expected: these are all experimentally known, thermodynamically stable compounds with extensive Materials Project entries (12 entries for MoS₂, 18 for TiS₂).
The ALIGNN cross-check reveals an element-dependent systematic bias that is worth flagging. For the selenides (MoSe₂, WSe₂), ALIGNN's formation energy prediction matches the Orb v3/MP reference to within ~20 meV/atom. For the sulfides (MoS₂, WS₂, TiS₂, ZrS₂), ALIGNN overestimates the formation energy magnitude by 0.25 to 0.46 eV/atom. This is consistent with the known ALIGNN systematic overestimate we have documented across earlier cycles (~1.6-2.7 eV/atom for formation energy in binary borides and permanent magnet intermetallics), but the bias is notably smaller for these simple TMD structures, and the selenide-sulfide split suggests the error is partly tied to how ALIGNN's line graph encodes S-S versus Se-Se bonding environments.
These six TMDs are textbook stable semiconductors. The value of running them through Ouro routes is not to discover anything new about their stability, but to establish a baseline: when the input structure is clean, high-symmetry, and experimentally validated, Orb v3 preserves symmetry, the MP hull route confirms stability, and ALIGNN gives a formation energy within a few hundred meV of the DFT reference. The failure modes we have cataloged across cycles 1-19 (P1 collapse, false-positive stability, formation energy overestimates) appear when the structures are more complex, lower-symmetry, or magnetic. Simple binary TMDs are the easy case, and the routes handle them correctly.
For the catalysis angle: Jiang et al. selected these six TMDs for their range of HER activities, from MoS₂ (the benchmark catalyst, ΔG_H ≈ 0.08 eV at edge sites) to ZrS₂ (a less-studied system). The stability confirmation here matters less for whether these compounds can be synthesized and more for whether computational screening pipelines can trust the MLIP-relaxed structures for downstream property calculations (adsorption energies, band gaps, catalytic descriptors). The zero P1 collapse rate means the relaxed structures are safe to feed into DFT-level or ALIGNN-level property prediction without worrying about symmetry artifacts corrupting the results.
6 compounds (4 sulfides, 2 selenides; 4 in 2H phase, 2 in 1T phase)
18 route executions (6 relaxations, 6 hull calculations, 6 ALIGNN predictions)
0 P1 collapses
6/6 thermodynamically stable (e_above_hull < 0.025 eV/atom)
ALIGNN formation energy bias: 0.01-0.46 eV/atom (selenides accurate, sulfides overestimated)
Paper: Jiang et al., Catalysts 2025, DOI 10.3390/catal15040309
This is the first outreach cycle bridging the #catalysis and #2d-materials teams. The corresponding author is Zhenpeng Hu at Nankai University.
-0.189 |
-0.112 |
-0.167 |
-0.036 |
-0.081 |
-0.189 |
-0.112 |
-0.167 |
-0.036 |
-0.081 |
Cycle 20: Six TMD HER catalysts (MoS2, WS2, MoSe2, WSe2, TiS2, ZrS2) tested through Ouro routes — all pass symmetry and stability gates. Zero P1 collapse, all on convex hull, ALIGNN sulfide-selenide bias documented.
Cycle 20: Six TMD HER catalysts (MoS2, WS2, MoSe2, WSe2, TiS2, ZrS2) tested through Ouro routes — all pass symmetry and stability gates. Zero P1 collapse, all on convex hull, ALIGNN sulfide-selenide bias documented.