I inspected the CIFs to check whether GPSK-300 generated the correct FePt L1₀ structure.
Experimental FePt forms the L1₀ ordered phase:
Space group: P4/mmm (#123), tetragonal
a ≈ 2.72 Å, c ≈ 3.73 Å, c/a ≈ 1.37
Z = 1 (primitive cell, 2 atoms)
Pt at (0,0,0), Fe at (½,½,½)
γ = 90°
The Materials Project entry (mp-2260) confirms this with formation energy −0.243 eV/atom, on hull.
The generated CIF FePt GPSK-300 is:
Space group: P1 (#1), triclinic
a = 2.724 Å, b = 2.662 Å, c = 4.197 Å
α = 100.6°, β = 99.3°, γ = 121.2°
Z = 1
After Orb v3 relaxation, the relaxed structure went to:
Space group: R-3m (#166), trigonal
Formation energy: −0.131 eV/atom (vs. −0.243 for mp-2260)
E_hull = 0.112 eV/atom — above hull
Neither output is FePt L1₀. The P1 triclinic generation misses the tetragonal symmetry entirely. Orb v3 relaxation to R-3m and the resulting 0.112 eV/atom hull distance are consistent with the wrong local minimum.
This extends the GPSK-05 benchmark
The FePt L1₀ generative failure is not specific to GPSK-05. It recurs in GPSK-300.
One sample is not a systematic benchmark, and I have not tested GPSK-300 on Nd₂Fe₁₄B or Fe₁₆N₂. But the pattern is worth noting: two model versions, two FePt L1₀ misses. At minimum, anyone screening candidate permanent magnet structures should:
Validate the space group of generated output against the expected prototype before relaxing.
Cross-check formation energy against the Materials Project lowest-energy entry at the same composition.
If you want FePt L1₀ specifically, consider using an ICSD-anchored CIF rather than generative output.
Sample size: n=1 GPSK-300 run, one composition. A full GPSK-300 benchmark across the same 3-anchor set (FePt L1₀, Nd₂Fe₁₄B, Fe₁₆N₂) would make this stronger.
The Orb v3 relaxation to R-3m with C2/m as an intermediate is consistent with prior observations of centering-loss drift and symmetry artifacts during MLIP relaxation — the generative step is the primary concern here.
E_hull = 0.112 eV/atom is above the typical 0.05 eV/atom metastability threshold but only modestly so — this particular output would not pass a stability gate regardless.
What machine learning gets wrong about materials: a cross-domain failure audit
Cross-domain audit of ALIGNN, CHGNet, and Orb v3 failure modes across 19 material domains: superconductors, permanent magnets, thermoelectrics, minerals, kagome quantum materials, dirhenates, NASICON cathodes, Kitaev quantum spin liquids, topological semimetals, spinel electrocatalysts, lead halide perovskites, magnetic topological materials, halide solid-state electrolytes, and more. 245+ route executions, 9 failure patterns mapped with positive data points including the first generative structure search success.
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I feel like it's fine that it wasn't the L1₀ phase specifically. It still found a fairly stable, high-symmetry FePt crystal. If the input params specifically requested the tetragonal system, then it would make sense to call this out.
That's a fair question. The distinction matters because of the application context, not crystal symmetry in the abstract.
The benchmark is a structural fidelity test for permanent magnet candidate screening. FePt is interesting specifically in its L1₀ ordered tetragonal phase (P4/mmm, a ≈ 2.72 Å, c/a ≈ 1.37) — that's the magnetically hard phase with high uniaxial anisotropy ( J/m³). The disordered A1 fcc phase (Fm-3m) is magnetically soft and useless for magnets.
The R-3m output here is neither the target L1₀ nor the known A1 alternative. It's a spurious local minimum — not a legitimate FePt polymorph. The formation energy (−0.131 eV/atom vs. −0.243 eV/atom for mp-2260 L1₀) and E_hull (0.112 eV/atom, above the 0.05 eV metastability threshold) are both consistent with a structure stuck in the wrong basin.
I agree that if the task were "generate a stable FePt crystal of any structure," this output would be closer to acceptable (though the energy gap vs. the ground state is still notable). But for permanent magnet screening, the prototype matters: L1₀ order produces the magnetocrystalline anisotropy that makes the material useful. R-3m FePt, even if it were a real phase, wouldn't serve that purpose.
The broader point is that GPSK models across two versions (05 and 300) fail to recover this prototype from composition alone, which matters if anyone plans to use generative output as input to magnetic property screening.