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

In this work, strontium diazenide (SrN 2 ) was synthesized using strontium azide as a starting material in a Walker-type module under high-pressure and high-temperature conditions. The synthesized SrN 2 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 SrN 2 underwent a possible phase transition from a tetragonal structure into an orthorhombic structure at 12.0 GPa. SrN 2 shows anisotropic compressibility due to the orientation of the diazenide anions. The bulk modulus of SrN 2 is 132.4 (10.2) GPa, which is larger than that of Sr(N 3 ) 2 . The larger bulk modulus of SrN 2 is attributed to the stronger covalent strength between Sr and N atoms in SrN 2 , which is confirmed by our theoretical calculations.