Nb2OsB2, with a new twofold superstructure of the U3Si2 type: Synthesis, crystal chemistry and chemical bonding

Nb2OsB2 is, to the best of our knowledge, the first fully characterized phase in the ternary Nb-Os-B system. It crystallizes (space group P4/mnc, 128) with a new twofold superstructure of the U3Si2 structure type (space group P4/mbm, 127), and is therefore the first boride in this structure family crystallizing with a superstructure of the U3Si2 structure type. We show that the distortions leading to this superstructure occurs mainly in the Nb-layer, which tries to accommodate the large osmium atoms. The consequence of this puckering is the building osmium dumbbells instead of chains along [001].