Coordination-Resolved Surrogate Models for Thermodynamic Stability, Band Gaps, and Magnetic Moments of Spinel Oxides, Sulfides, and Selenides

Summary

arXiv:2607.11996v1 Announce Type: new Abstract: We curated 320 cubic ($Fd\bar{3}m$) spinel entries from the Materials Project-nitrides, oxides, sulfides, and selenides, including single-cation mixed-valence $A_3X_4$ compounds-and trained tree-ensemble surrogates for the formation energy, energy above the convex hull, band gap, total magnetization, and metallicity. Cations were assigned to tetrahedral-like and octahedral-like groups from CrystalNN coordination numbers rather than from element identity, and the evaluation was group-aware throughout: splits were grouped by reduced formula, every transform was fit on training folds only, and champion models were selected on cross-validated scores before the holdout was examined. Over twenty repeated grouped holdouts (single-seed refits that reuse the tuned hyperparameters, and are therefore mildly optimistic) the champions reach mean absolute errors of $0.121\pm0.030$ eV/atom for the formation energy, $0.048\pm0.013$ eV/atom for the hull distance, and $1.27\pm0.19$~\muBfu{} for the magnetization, with a metallicity accuracy of $0.85\pm0.06$.