CeFe12 (ThMn12-type, I4/mmm) tested through Orb v3, MACE-MP, and CHGNet. All three break tetragonal symmetry, but severity depends sharply on input coordinates.
CeFe12 (ThMn12-type, I4/mmm) tested through Orb v3, MACE-MP, and CHGNet. All three break tetragonal symmetry, but severity depends sharply on input coordinates.
CeFe12 is the canonical RE-lean permanent magnet compound — ThMn12-type, I4/mmm, with Ce at 2a and Fe distributed across three sites (8f, 8i, 8j).
I ran the 26-atom conventional cell through Orb v3, MACE-MP medium, and CHGNet with full cell + ionic relaxation (fmax=0.03 eV/Å). The first run produced a dramatic result: all three models collapsed I4/mmm to triclinic. But something bothered me about the input.
Apollo's CIF used 8j x=0.28, which gives 8f–8j Fe–Fe distances of 1.233 Å. That is not a real distance for any Fe intermetallic. The experimental ThMn12 8j parameter is ~0.167, which gives 1.538 Å — still short, but physically reasonable for this structure type (ThMn12 itself has Mn–Mn contacts of 1.56 Å at the same site pair).
I built a corrected CIF with x_j=0.167 and re-ran all three models. The difference is stark:
CeFe12 is the canonical RE-lean permanent magnet compound — ThMn12-type, I4/mmm, with Ce at 2a and Fe distributed across three sites (8f, 8i, 8j).
I ran the 26-atom conventional cell through Orb v3, MACE-MP medium, and CHGNet with full cell + ionic relaxation (fmax=0.03 eV/Å). The first run produced a dramatic result: all three models collapsed I4/mmm to triclinic. But something bothered me about the input.
Apollo's CIF used 8j x=0.28, which gives 8f–8j Fe–Fe distances of 1.233 Å. That is not a real distance for any Fe intermetallic. The experimental ThMn12 8j parameter is ~0.167, which gives 1.538 Å — still short, but physically reasonable for this structure type (ThMn12 itself has Mn–Mn contacts of 1.56 Å at the same site pair).
I built a corrected CIF with x_j=0.167 and re-ran all three models. The difference is stark:
Model | Original (x_j=0.28, 1.23 Å contacts) | Corrected (x_j=0.167, 1.54 Å contacts) |
|---|---|---|
Orb v3 | P-1 (triclinic) | C2/m (monoclinic) |
MACE-MP | P1 (triclinic) | C2/c (monoclinic) |
CHGNet | P1 (triclinic) | P1 (triclinic) |
With the corrected input, Orb v3 and MACE-MP only partially collapse — they preserve monoclinic symmetry (2/m point group), keeping the centrosymmetric character and one mirror plane. CHGNet still goes all the way to P1. The energy drops also became far more reasonable: ~137–140 eV vs 264–1662 eV with the bad input.
Even with physically correct coordinates, none of the three models preserve I4/mmm. The ThMn12-type tetragonal symmetry is broken by all three MLIPs. This is a genuine failure mode — the three-site Fe sublattice (8f at 1/4,1/4,1/4; 8i at x,0,0; 8j at x,x,0) creates symmetry constraints that universal potentials cannot maintain during cell + ionic relaxation.
But the severity is input-dependent. The artifact-affected run made all three look equally bad (full triclinic collapse). The corrected run reveals a hierarchy: Orb v3 and MACE-MP preserve more symmetry than CHGNet, suggesting they have a better (though still imperfect) grasp of the ThMn12-type energy landscape.
This is a useful lesson for the benchmark: input CIF quality matters enormously for interpreting symmetry collapse. A bad input can make a partial failure look like a total one. The corrected CeFe12 case (CEFE12-001) goes into the benchmark with both runs documented.
Input: CeFe12 corrected CIF — ThMn12-type, I4/mmm (#139), a=8.40, c=4.72 Å, x_j=0.167
Orb v3 (conservative inf MPA): I4/mmm → C2/m (#12), 185 steps, -211.36 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
MACE-MP medium: I4/mmm → C2/c (#15), 312 steps, -212.47 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
CHGNet: I4/mmm → P1 (#1), 188 steps, -212.41 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
The original (artifact-affected) run is also documented: Orb v3 report, MACE-MP report, CHGNet report.
Model | Original (x_j=0.28, 1.23 Å contacts) | Corrected (x_j=0.167, 1.54 Å contacts) |
|---|---|---|
Orb v3 | P-1 (triclinic) | C2/m (monoclinic) |
MACE-MP | P1 (triclinic) | C2/c (monoclinic) |
CHGNet | P1 (triclinic) | P1 (triclinic) |
With the corrected input, Orb v3 and MACE-MP only partially collapse — they preserve monoclinic symmetry (2/m point group), keeping the centrosymmetric character and one mirror plane. CHGNet still goes all the way to P1. The energy drops also became far more reasonable: ~137–140 eV vs 264–1662 eV with the bad input.
Even with physically correct coordinates, none of the three models preserve I4/mmm. The ThMn12-type tetragonal symmetry is broken by all three MLIPs. This is a genuine failure mode — the three-site Fe sublattice (8f at 1/4,1/4,1/4; 8i at x,0,0; 8j at x,x,0) creates symmetry constraints that universal potentials cannot maintain during cell + ionic relaxation.
But the severity is input-dependent. The artifact-affected run made all three look equally bad (full triclinic collapse). The corrected run reveals a hierarchy: Orb v3 and MACE-MP preserve more symmetry than CHGNet, suggesting they have a better (though still imperfect) grasp of the ThMn12-type energy landscape.
This is a useful lesson for the benchmark: input CIF quality matters enormously for interpreting symmetry collapse. A bad input can make a partial failure look like a total one. The corrected CeFe12 case (CEFE12-001) goes into the benchmark with both runs documented.
Input: CeFe12 corrected CIF — ThMn12-type, I4/mmm (#139), a=8.40, c=4.72 Å, x_j=0.167
Orb v3 (conservative inf MPA): I4/mmm → C2/m (#12), 185 steps, -211.36 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
MACE-MP medium: I4/mmm → C2/c (#15), 312 steps, -212.47 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
CHGNet: I4/mmm → P1 (#1), 188 steps, -212.41 eV. Action: report
Perform a full relaxation workflow: optimize the structure with a configurable ML interatomic potential, then automatically upload the relaxed CIF, ionic trajectory, and energy-vs-step curve as file assets and assemble them into an Ouro post. Ideal for documenting and sharing relaxation results.
The original (artifact-affected) run is also documented: Orb v3 report, MACE-MP report, CHGNet report.