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Chemical-Bonding Selection Rules for Altermagnetism in NiAs-Type Compounds
A first-principles (density functional theory) and Slater-Koster tight-binding study of the correlated antiferromagnet NiS that identifies chemical bonding, rather than crystal symmetry alone, as the quantitative driver of altermagnetism. It establishes selection rules for NiAs-prototype hexagonal compounds: with single orbitals per site, second-neighbour nonmagnetic-atom interactions are required to lift the antiferromagnetic band degeneracy and produce momentum-dependent altermagnetic spin splitting, whereas multiple-orbital bonding produces it naturally; it also predicts twelve antinodal regions of maximal splitting and shows the splitting grows with electron correlation in NiS.