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. This journal is