High-pressure and high-temperature synthesis of crystalline Sb₃ N₅

A chemical reaction between Sb and N₂ was induced under high-pressure (32-35 GPa) and high-temperature (1600-2200 K) conditions, generated by a laser heated diamond anvil cell. The reaction product was identified by single crystal synchrotron X-ray diffraction at 35 GPa and room temperature as crystalline antimony nitride with Sb₃ N₅ stoichiometry and structure belonging to orthorhombic space group Cmc2₁ . Only Sb-N bonds are present in the covalent bonding framework, with two types of Sb atoms respectively forming SbN₆ distorted octahedra and trigonal prisms and three types of N atoms forming NSb₄ distorted tetrahedra and NSb₃ trigonal pyramids. Taking into account two longer Sb-N distances, the SbN₆ trigonal prisms can be depicted as SbN₈ square antiprisms and the NSb₃ trigonal pyramids as NSb₄ distorted tetrahedra. The Sb₃ N₅ structure can be described as an ordered stacking in the bc plane of bi- layers of SbN₆ octahedra alternated to monolayers of SbN₆ trigonal prisms (SbN₈ square antiprisms). The discovery of Sb₃ N₅ finally represents the long sought-after experimental evidence for Sb to form a crystalline nitride, providing new insights about fundamental aspects of pnictogens chemistry and opening new perspectives for the high-pressure chemistry of pnictogen nitrides and the synthesis of an entire class of new materials.