High-pressure and high-temperature synthesis of crystalline Sb 3 N 5 .

A chemical reaction between Sb and N 2 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 Sb 3 N 5 stoichiometry and structure belonging to orthorhombic space group Cmc2 1 . Only Sb-N bonds are present in the covalent bonding framework, with two types of Sb atoms respectively forming SbN 6 distorted octahedra and trigonal prisms and three types of N atoms forming NSb 4 distorted tetrahedra and NSb 3 trigonal pyramids. Taking into account two longer Sb-N distances, the SbN 6 trigonal prisms can be depicted as SbN 8 square antiprisms and the NSb 3 trigonal pyramids as NSb 4 distorted tetrahedra. The Sb 3 N 5 structure can be described as an ordered stacking in the bc plane of bi- layers of SbN 6 octahedra alternated to monolayers of SbN 6 trigonal prisms (SbN 8 square antiprisms). The discovery of Sb 3 N 5 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.