A Novel High-Pressure Tin Oxynitride Sn₂ N₂ O

We report the first oxynitride of tin, Sn₂ N₂ O (SNO), exhibiting a Rh₂ S₃ -type crystal structure with space group Pbcn. All Sn atoms are in six-fold coordination, in contrast to Si in silicon oxynitride (Si₂ N₂ O) and Ge in the isostructural germanium oxynitride (Ge₂ N₂ O), which appear in four-fold coordination. SNO was synthesized at 20 GPa and 1200-1500 °C in a large volume press. The recovered samples were characterized by synchrotron powder X-ray diffraction and single-crystal electron diffraction in the TEM using the automated diffraction tomography (ADT) technique. The isothermal bulk modulus was determined as B_o =193(5) GPa by using in-situ synchrotron X-ray diffraction in a diamond anvil cell. The structure model is supported by DFT calculations. The enthalpy of formation, the bulk modulus, and the band structure have been calculated.