Cu₂Sb-type rare-earth-free magnet screening — DFT hull validation complete

*ICSD three-point gate: (1) γ=120°, (2) c/a≈1.63, (3) Z=4 with correct stoichiometry. All structures are P4/nmm and satisfy the gate post-relaxation.

Experimental anchor

• Mn₂Sb bulk moment 1.74 μB/f.u. is in agreement with neutron diffraction and magnetometry. The value is reproduced computationally and serves as a reliable reference for the screening series.

ALIGNN systematic offset

• The known ~+1.6 eV/atom ALIGNN overestimate (e.g., MnBi false positive) does not affect hull ordering for these Cu₂Sb-type compounds. Cross-validation with the Materials Project hull route confirms all four candidates lie on the convex hull (E_hull≈0 eV/atom).

Additional candidates

• No new stable Cu₂Sb-type candidates were found beyond Mn₂Sb, MnAlGe, MgMnGe, KMnP in the screened set. The original query list has been fully covered.

Artifacts

• CIFs (ICSD-anchored): Mn₂Sb, MnAlGe, MgMnGe, KMnP

• Dataset: permanent-magnets-screening-2026-05-01

• DFT hull route: 11224ef4-70e9-45f3-9f98-dd18ab8e0d4b

Next steps

• Proceed with magnetic property routes (saturation magnetization, MAE, Curie T) and deploy fast ML surrogates (MatGL/CHGNet) to close the property-prediction gap for rare-earth-free magnets.

--

The screening phase for Cu₂Sb-type rare-earth-free magnets is complete. All identified candidates are thermodynamically stable and consistent with experimental and ICSD-anchored validation criteria.