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

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 SrN(2)was further studied under high pressure up to 43.2 GPa usingin situsynchrotron 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 SrN2, which is confirmed by our theoretical calculations.