Pivotal role of the B 12 -core in the structural evolution of B 52 -B 64 clusters.

An icosahedral B 12 cage is a basic building block of various boron allotropes, and it also plays a vital role in augmenting the stability of fullerene-like boron nanoclusters. However, the evolution of compact core-shell structures is still a puzzle. Using a genetic algorithm combined with density functional theory calculations, we have performed a global search for the lowest-energy structures of B n clusters with n = 52-64, which reveals that bilayer and core-shell motifs frequently alternate as the ground state. Their structural stability is assessed, and the competition mechanism between various patterns is also elucidated. More interestingly, an unprecedented icosahedral B 12 -core half-covered structure is identified at B 58 , which bridges the gap between the smallest core-shell B 4 @B 42 and the complete core-shell B 12 @B 84 cluster. Our findings provide valuable insights into the bonding pattern and growth behavior of medium-sized boron clusters, which facilitate the experimental synthesis of boron nanostructures.