Structural Diversity and Multicenter Bonding in Beryllium-Osmium Intermetallic Compounds.

Beryllium intermetallic compounds (beryllides) have attracted considerable interest for applications relevant to nuclear systems, refractory materials, and aerospace systems due to their exceptional physical properties. In this work, crystal structures of osmium beryllides were systematically explored using a combination of global structure searching and first-principles methods, and their bonding characteristics and mechanical properties were investigated in detail. In addition to the known Be17Os3 phase, six new compounds, namely, Be12Os, Be4Os, Be7Os2, Be3Os, Be2Os and BeOs2, were predicted to be thermodynamically stable over specific pressure ranges. As the Be content decreases, the Be sublattice evolves from three-dimensional frameworks to quasi-two-dimensional networks, then to a fully two-dimensional layered structure, and ultimately to isolated Be atoms. Electronic structure analyses reveal that bonding in these compounds is governed by multicenter covalent interactions, including Be6 "gold-ingot" clusters, Be5 trigonal bipyramids and Os-containing units (BexOsy, x = 2-4; y = 1-2). Notably, Be3Os is identified as a rare semiconducting beryllide with an indirect band gap (0.62 eV, HSE06+SOC), while Be2Os exhibits a ductile mechanical response. Together, our findings underscore that multicenter bonding governs the structure-property relationships in osmium beryllides and offer theoretical guidance for the design of advanced beryllium-based materials.