Unveiling the Inverse Sandwich Cr 2 B 6 Building Block for Self-Assembled Antiferromagnetic Nanowires in Cr 2 B n ( n = 3–12) Clusters

Dual-transition-metal-doped boron clusters have garnered growing research interest owing to their unique bonding patterns and distinctive electronic/magnetic properties. In this work, we investigated the structural evolution, bonding characteristics, and electronic and magnetic properties of Cr₂B_n (n = 3-12) clusters through a hybrid global search algorithm and density functional theory calculations. It was found that small-sized Cr₂B_n (n = 3-5) clusters adopt quasi-planar structures; those with n = 6-8 form inverse sandwich configurations, while larger clusters (n = 9-12) exhibit extended inverse sandwich-based structures. In all Cr₂B_n (n = 3-12) clusters, the two Cr atoms exhibit opposite magnetic moments greater than 3 μ_B. The Cr₂B₆ cluster exhibits a considerable HOMO-LUMO gap (3.554 eV) and dual σ- and π-aromaticity, indicative of its high stability. Two self-assembled 1D nanowires derived from the inverse sandwich Cr₂B₆ structure are antiferromagnetic semiconductors that exhibit indirect and direct band gaps of 2.03 and 0.80 eV, respectively.