Synthesis and high-pressure studies of strontium diazenide by synchrotron X-ray diffraction and DFT calculations

Abstract

In this work, strontium diazenide (SrN₂) was synthesized using strontium azide as a starting material in a Walker-type module under high-pressure and high-temperature conditions. The synthesized SrN₂ was further studied under high pressure up to 43.2 GPa using in situ synchrotron X-ray diffraction to supplement the high-pressure exploration of alkaline earth diazenides. The SrN₂ underwent a possible phase transition from a tetragonal structure into an orthorhombic structure at 12.0 GPa. SrN₂ shows anisotropic compressibility due to the orientation of the diazenide anions. The bulk modulus of SrN₂ is 132.4 (10.2) GPa, which is larger than that of Sr(N₃)₂. The larger bulk modulus of SrN₂ is attributed to the stronger covalent strength between Sr and N atoms in SrN₂, which is confirmed by our theoretical calculations.